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MWP Issue 02 File 04
THE MWP FILES
-------------
File #4 of
Issue #2
Summer of '97
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Article by:SunOS staff.
"rlogin, sulogin, passwd, ksh.-MAN files."
Note:The following sections are excerpts of UNIX man files. The following
man files are included,
rlogin
sulogin
passwd
ksh
The purpose of this article is to show how the above services are used in a
very CORRECT manner.
RLOGIN
------
rlogin(1) User Commands rlogin(1)
NAME
rlogin - remote login
SYNOPSIS
rlogin [ -L ] [ -8 ] [ -ec ] [ -l username ] hostname
AVAILABILITY
SUNWcsu
DESCRIPTION
rlogin establishes a remote login session from your terminal
to the remote machine named hostname.
Hostnames are listed in the hosts database, which may be
contained in the /etc/hosts file, the Network Information
Service (NIS) hosts map, the Internet domain name server, or
a combination of these. Each host has one official name
(the first name in the database entry), and optionally one
or more nicknames. Either official hostnames or nicknames
may be specified in hostname.
Each remote machine may have a file named /etc/hosts.equiv
containing a list of trusted hostnames with which it shares
usernames. Users with the same username on both the local
and remote machine may rlogin from the machines listed in
the remote machine's /etc/hosts.equiv file without supplying
a password. Individual users may set up a similar private
equivalence list with the file .rhosts in their home direc-
tories. Each line in this file contains two names: a host-
name and a username separated by a space. An entry in a re-
mote user's .rhosts file permits the user named username who
is logged into hostname to log in to the remote machine as
the remote user without supplying a password. If the name
of the local host is not found in the /etc/hosts.equiv file
on the remote machine, and the local username and hostname
are not found in the remote user's .rhosts file, then the
remote machine will prompt for a password. Hostnames listed
in /etc/hosts.equiv and .rhosts files must be the official
hostnames listed in the hosts database; nicknames may not be
used in either of these files.
For security reasons, the .rhosts file must be owned by ei-
ther the remote user or by root.
The remote terminal type is the same as your local terminal
type (as given in your environment TERM variable). The ter-
minal or window size is also copied to the remote system if
the server supports the option, and changes in size are re-
flected as well. All echoing takes place at the remote
site, so that (except for delays) the remote login is tran-
sparent. Flow control using CTRL-S and CTRL-Q and flushing
of input and output on interrupts are handled properly.
SunOS 5.5.1 Last change: 13 Dec 1995 1
rlogin(1) User Commands rlogin(1)
OPTIONS
-L Allow the rlogin session to be run in "li-
tout" mode.
-8 Pass eight-bit data across the net instead
of seven-bit data.
-ec Specify a different escape character, c, for
the line used to disconnect from the remote
host.
-l username Specify a different username for the remote
login. If you do not use this option, the
remote username used is the same as your lo-
cal username.
Escape Sequences
Lines that you type which start with the tilde character are
"escape sequences" (the escape character can be changed us-
ing the -e options):
~. Disconnect from the remote host - this is not the same
as a logout, because the local host breaks the connec-
tion with no warning to the remote end.
~susp
Suspend the login session (only if you are using a
shell with Job Control). susp is your "suspend" char-
acter, usually CTRL-Z; see tty(1).
~dsusp
Suspend the input half of the login, but output will
still be seen (only if you are using a shell with Job
Control). dsusp is your "deferred suspend" character,
usually CTRL-Y; see tty(1).
FILES
/etc/passwd contains information about users' ac-
counts
/usr/hosts/* for hostname version of the command
/etc/hosts.equiv
list of trusted hostnames with shared
usernames
/etc/nologin message displayed to users attempting to
login during machine shutdown
$HOME/.rhosts private list of trusted
hostname/username combinations
SEE ALSO
rsh(1), stty(1), tty(1), in.named(1M), hosts(4),
SunOS 5.5.1 Last change: 13 Dec 1995 2
rlogin(1) User Commands rlogin(1)
hosts.equiv(4), nologin.4
DIAGNOSTICS
NO LOGINS: System going down in N minutes
The machine is in the process of being
shutdown and logins have been disabled.
NOTES
When a system is listed in hosts.equiv, its security must be
as good as local security. One insecure system listed in
hosts.equiv can compromise the security of the entire sys-
tem.
The Network Information Service (NIS) was formerly known as
Sun Yellow Pages (YP). The functionality of the two remains
the same; only the name has changed.
This implementation can only use the TCP network service.
SULOGIN
-------
sulogin(1M) Maintenance Commands sulogin(1M)
NAME
sulogin - access single-user mode
SYNOPSIS
sulogin
AVAILABILITY
SUNWcsr
DESCRIPTION
sulogin is automatically invoked by init when the system is
first started. It prompts the user to type the root pass-
word to enter system maintenance mode (single-user mode) or
to type EOF (typically CTRL-D) for normal startup (multi-
user mode). sulogin should never be directly invoked by the
user.
FILES
/etc/sulogin
SEE ALSO
init(1M)
PASSWD
------
passwd(1) User Commands passwd(1)
NAME
passwd - change login password and password attributes
SYNOPSIS
passwd [ name ]
passwd -r files [ -egh ] [ name ]
passwd -r files -s [ -a ]
passwd -r files -s [ name ]
passwd -r files [ -d | -l ] [ -f ] [ -n min ] [ -w warn ]
[ -x max ] name
passwd -r nis [ -egh ] [ name ]
passwd -r nisplus [ -egh ] [ -D domainname ] [ name ]
passwd -r nisplus -s [ -a ]
passwd -r nisplus [ -D domainname ] -s [ name ]
passwd -r nisplus [ -l ] [ -f ] [ -n min ] [ -w warn ]
[ -x max ] [ -D domainname ] name
AVAILABILITY
SUNWcsu
DESCRIPTION
The passwd command changes the password or lists password
attributes associated with the user's login name. Addition-
ally, privileged users may use passwd to install or change
passwords and attributes associated with any login name.
When used to change a password, passwd prompts everyone for
their old password, if any. It then prompts for the new
password twice. When the old password is entered, passwd
checks to see if it has "aged" sufficiently. If "aging" is
insufficient, passwd terminates; see pwconv(1M), nist-
bladm(1), and shadow(4) for additional information. The
pwconv command creates and updates /etc/shadow with informa-
tion from /etc/passwd. pwconv relies on a special value of
'x' in the password field of /etc/passwd. This value of 'x'
indicates that the password for the user is already in
/etc/shadow and should not be modified.
If aging is sufficient, a check is made to ensure that the
new password meets construction requirements. When the new
password is entered a second time, the two copies of the new
password are compared. If the two copies are not identical
the cycle of prompting for the new password is repeated for
SunOS 5.5.1 Last change: 18 Oct 1995 1
passwd(1) User Commands passwd(1)
at most two more times.
Passwords must be constructed to meet the following require-
ments:
o Each password must have PASSLENGTH characters, where
PASSLENGTH is defined in /etc/default/passwd and is
set to 6. Only the first eight characters are signi-
ficant.
o Each password must contain at least two alphabetic
characters and at least one numeric or special char-
acter. In this case, "alphabetic" refers to all
upper or lower case letters.
o Each password must differ from the user's login name
and any reverse or circular shift of that login name.
For comparison purposes, an upper case letter and its
corresponding lower case letter are equivalent.
o New passwords must differ from the old by at least
three characters. For comparison purposes, an upper
case letter and its corresponding lower case letter
are equivalent.
If all requirements are met, by default, the passwd command
will consult /etc/nsswitch.conf to determine in which repo-
sitories to perform password update. It searches the passwd
and passwd_compat entries. The sources (repositories) asso-
ciated with these entries will be updated. However, the
password update configurations supported are limited to the
following 5 cases. Failure to comply with the configura-
tions will prevent users from logging onto the system.
o passwd: files
o passwd: files nis
o passwd: files nisplus
o passwd: compat (==> files nis)
o passwd: compat (==> files nisplus)
passwd_compat: nisplus
Network administrators, who own the NIS+ password table, may
change any password attributes.
In files case, super-users (for instance, real and effective
uid equal to zero, see id(1M) and su(1M)) may change any
password; hence, passwd does not prompt privileged users for
the old password. Privileged users are not forced to comply
with password aging and password construction requirements.
A privileged user can create a null password by entering a
carriage return in response to the prompt for a new pass-
word. (This differs from passwd -d because the "password"
SunOS 5.5.1 Last change: 18 Oct 1995 2
passwd(1) User Commands passwd(1)
prompt will still be displayed.)
Any user may use the -s option to show password attributes
for his or her own login name. Provided they are using the
-r nisplus argument. Otherwise the - s argument is res-
tricted to the super-user.
The format of the display will be:
name status mm/dd/yy min max warn
or, if password aging information is not present,
name status
where
name The login ID of the user.
status The password status of name: PS stands for
passworded or locked, LK stands for locked, and
NP stands for no password.
mm/dd/yy
The date password was last changed for name.
(Note that all password aging dates are deter-
mined using Greenwich Mean Time (Universal
Time) and, therefore, may differ by as much as
a day in other time zones.)
min The minimum number of days required between
password changes for name. MINWEEKS is found
in /etc/default/passwd and is set to NULL.
max The maximum number of days the password is
valid for name. MAXWEEKS is found in
/etc/default/passwd and is set to NULL.
warn The number of days relative to max before the
password expires and the name will be warned.
OPTIONS
-r Specifies the repository to which an opera-
tion is applied. The supported repositories
are files, nis, or nisplus.
-e Change the login shell.
-g Change the gecos (finger) information.
-h Change the home directory.
SunOS 5.5.1 Last change: 18 Oct 1995 3
passwd(1) User Commands passwd(1)
-D domainname Consult the passwd.org_dir table in domain-
name. If this option is not specified, the
default domainname returned by
nis_local_directory(3N) will be used. This
domain name is the same as that returned by
domainname(1M).
-s name Show password attributes for the login name.
For the nisplus repository, this works for
everyone. However for the files repository,
this only works for the super-user. It does
not work at all for the nis repository which
does not support password aging.
-a Show password attributes for all entries.
Use only with the -s option; name must not be
provided. For nisplus repository, this will
show only the entries in the NIS+ passwd
table in the local domain that the invoker is
authorized to "read". For the files reposi-
tory, this is restricted to the super-user.
Privileged User Options
Only a privileged user can use the following options:
-f Force the user to change password at the
next login by expiring the password for name.
-l Locks password entry for name.
-n min Set minimum field for name. The min field
contains the minimum number of days between
password changes for name. If min is greater
than max, the user may not change the pass-
word. Always use this option with the - x
option, unless max is set to -1 (aging turned
off). In that case, min need not be set.
-w warn Set warn field for name. The warn field
contains the number of days before the pass-
word expires and the user is warned. This
option is not valid if password aging is dis-
abled.
-x max Set maximum field for name. The max field
contains the number of days that the password
is valid for name. The aging for name will
be turned off immediately if max is set to -
1. If it is set to 0, then the user is
forced to change the password at the next
login session and aging is turned off.
SunOS 5.5.1 Last change: 18 Oct 1995 4
passwd(1) User Commands passwd(1)
-d Deletes password for name. The login name
will not be prompted for password. It is
only applicable to the files repository.
ENVIRONMENT
If any of the LC_* variables ( LC_CTYPE, LC_MESSAGES,
LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY ) (see
environ(5)) are not set in the environment, the operational
behavior of passwd for each corresponding locale category is
determined by the value of the LANG environment variable.
If LC_ALL is set, its contents are used to override both the
LANG and the other LC_* variables. If none of the above
variables is set in the environment, the "C" (U.S. style)
locale determines how passwd behaves.
LC_CTYPE Determines how passwd handles characters.
When LC_CTYPE is set to a valid value, passwd
can display and handle text and filenames
containing valid characters for that locale.
passwd can display and handle Extended Unix
Code (EUC) characters where any individual
character can be 1, 2, or 3 bytes wide.
passwd can also handle EUC characters of 1,
2, or more column widths. In the "C" locale,
only characters from ISO 8859-1 are valid.
LC_MESSAGES Determines how diagnostic and informative
messages are presented. This includes the
language and style of the messages, and the
correct form of affirmative and negative
responses. In the "C" locale, the messages
are presented in the default form found in
the program itself (in most cases, U.S.
English).
EXIT STATUS
The passwd command exits with one of the following values:
0 success.
1 Permission denied.
2 Invalid combination of options.
3 Unexpected failure. Password file unchanged.
4 Unexpected failure. Password file(s) missing.
5 Password file(s) busy. Try again later.
6 Invalid argument to option.
7 Aging option is disabled.
FILES
/etc/oshadow
/etc/passwd password file.
/etc/shadow shadow password file.
/etc/default/passwd Default values can be set for the fol-
lowing flags in /etc/default/passwd.
SunOS 5.5.1 Last change: 18 Oct 1995 5
passwd(1) User Commands passwd(1)
For example: MAXWEEKS=26
MAXWEEKS Maximum time period that
password is valid.
MINWEEKS Minimum time period
before the password can
be changed.
PASSLENGTH Minimum length of pass-
word, in characters.
WARNWEEKS Time period until warning
of date of password's
ensuing expiration.
SEE ALSO
finger(1), login(1), nispasswd(1), nistbladm(1),
yppasswd(1), domainname(1M), eeprom(1M), id(1M),
passmgmt(1M), pwconv(1M), su(1M), useradd(1M), userdel(1M),
usermod(1M), crypt(3C), getpwnam(3C), getspnam(3C),
nis_local_directory(3N), loginlog(4), passwd(4), shadow(4),
environ(5)
NOTES
The passwd command replaces the nispasswd and yppasswd com-
mands and should be used in their place.
KSH
---
[3] drogers@cwis.net> man ksh
Reformatting page. Wait... done
ksh(1) User Commands ksh(1)
NAME
ksh, rksh - KornShell, a standard/restricted command and
programming language
SYNOPSIS
/usr/bin/ksh [ +-abCefhikmnoprstuvx ] [ +-o option ] ...
[ -c string ] [ arg... ]
/usr/xpg4/bin/sh [ +-abCefhikmnoprstuvx ] [ +-o option ] ...
[ -c string ] [ arg... ]
/usr/bin/rksh [ +-abCefhikmnoprstuvx ] [ +-o option ] ...
[ -c string ] [ arg... ]
AVAILABILITY
/usr/bin/ksh
/usr/bin/rksh
SUNWcsu
/usr/xpg4/bin/sh
SUNWxcu4
DESCRIPTION
/usr/xpg4/bin/sh is identical to /usr/bin/ksh, a command and
programming language that executes commands read from a ter-
minal or a file. rksh is a restricted version of the com-
mand interpreter ksh; it is used to set up login names and
execution environments whose capabilities are more con-
trolled than those of the standard shell. See Invocation
below for the meaning of arguments to the shell.
Definitions
A metacharacter is one of the following characters:
; & ( ) | < > NEWLINE SPACE TAB
A blank is a TAB or a SPACE. An identifier is a sequence of
letters, digits, or underscores starting with a letter or
underscore. Identifiers are used as names for functions and
variables. A word is a sequence of characters separated by
one or more non-quoted metacharacters.
A command is a sequence of characters in the syntax of the
shell language. The shell reads each command and carries
out the desired action either directly or by invoking
separate utilities. A special-command is a command that is
carried out by the shell without creating a separate pro-
cess. Except for documented side effects, most special com-
mands can be implemented as separate utilities.
Commands
A simple-command is a sequence of blank-separated words
SunOS 5.5.1 Last change: 2 Jan 1996 1
ksh(1) User Commands ksh(1)
which may be preceded by a variable assignment list. (See
Environment below.) The first word specifies the name of
the command to be executed. Except as specified below, the
remaining words are passed as arguments to the invoked com-
mand. The command name is passed as argument 0 (see
exec(2)). The value of a simple-command is its exit status
if it terminates normally, or (octal) 200+status if it ter-
minates abnormally (see signal(3C) for a list of status
values).
A pipeline is a sequence of one or more commands separated
by |. The standard output of each command but the last is
connected by a pipe(2) to the standard input of the next
command. Each command is run as a separate process; the
shell waits for the last command to terminate. The exit
status of a pipeline is the exit status of the last command.
A list is a sequence of one or more pipelines separated by
;, &, &&, or ||, and optionally terminated by ;, &, or |&.
Of these five symbols, ;, &, and |& have equal precedence,
which is lower than that of && and ||. The symbols && and |
| also have equal precedence. A semicolon (;) causes
sequential execution of the preceding pipeline; an ampersand
(&) causes asynchronous execution of the preceding pipeline
(that is, the shell does not wait for that pipeline to fin-
ish). The symbol |& causes asynchronous execution of the
preceding command or pipeline with a two-way pipe esta-
blished to the parent shell.
The standard input and output of the spawned command can be
written to and read from by the parent shell using the -p
option of the special commands read and print described in
Special Commands. The symbol && (||) causes the list fol-
lowing it to be executed only if the preceding pipeline
returns 0 (or a non-zero) value. An arbitrary number of
new-lines may appear in a list, instead of a semicolon, to
delimit a command.
A command is either a simple-command or one of the follow-
ing. Unless otherwise stated, the value returned by a com-
mand is that of the last simple-command executed in the com-
mand.
for identifier [ in word ... ] ; do list ; done
Each time a for command is executed, identifier is set
to the next word taken from the in word list. If in
word ... is omitted, then the for command executes the
do list once for each positional parameter that is set
(see Parameter Substitution below). Execution ends
when there are no more words in the list.
select identifier [ in word ... ] ; do list ; done
SunOS 5.5.1 Last change: 2 Jan 1996 2
ksh(1) User Commands ksh(1)
A select command prints to standard error (file
descriptor 2), the set of words, each preceded by a
number. If in word ... is omitted, then the posi-
tional parameters are used instead (see Parameter Sub-
stitution below). The PS3 prompt is printed and a line
is read from the standard input. If this line consists
of the number of one of the listed words, then the
value of the variable identifier is set to the word
corresponding to this number. If this line is empty
the selection list is printed again. Otherwise the
value of the variable identifier is set to NULL. (See
Blank Interpretation about NULL). The contents of the
line read from standard input is saved in the shell
variable REPLY. The list is executed for each selection
until a break or EOF is encountered. If the REPLY
variable is set to NULL by the execution of list, then
the selection list is printed before displaying the PS3
prompt for the next selection.
case word in [ pattern [ | pattern ] ) list ;; ] ... esac
A case command executes the list associated with the
first pattern that matches word. The form of the pat-
terns is the same as that used for file-name generation
(see File Name Generation below).
if list ; then list ;
[ elif list ; then list ; ... ] [ else list ; ] fi
The list following if is executed and, if it returns an
exit status of 0, the list following the first then is
executed. Otherwise, the list following elif is exe-
cuted and, if its value is 0, the list following the
next then is executed. Failing that, the else list is
executed. If no else list or then list is executed,
then the if command returns 0 exit status.
while list ; do list ; done
until list ; do list ; done
A while command repeatedly executes the while list and,
if the exit status of the last command in the list is
0, executes the do list; otherwise the loop terminates.
If no commands in the do list are executed, then the
while command returns 0 exit status; until may be used
in place of while to negate the loop termination test.
(list)
Execute list in a separate environment. Note, that if
two adjacent open parentheses are needed for nesting, a
space must be inserted to avoid arithmetic evaluation
as described below.
{list}
list is simply executed. Note that unlike the
SunOS 5.5.1 Last change: 2 Jan 1996 3
ksh(1) User Commands ksh(1)
metacharacters ( and ), { and } are reserved words and
must occur at the beginning of a line or after a ; in
order to be recognized.
[[expression]]
Evaluates expression and returns 0 exit status when
expression is true. See Conditional Expressions below,
for a description of expression.
function identifier { list ;}
identifier() { list ;}
Define a function which is referenced by identifier.
The body of the function is the list of commands
between { and }. (See Functions below).
time pipeline
The pipeline is executed and the elapsed time as well
as the user and system time are printed to standard
error.
The following reserved words are only recognized as the
first word of a command and when not quoted:
! if then else elif fi case esac for while until do done { }
function select time [[ ]]
Comments
A word beginning with # causes that word and all the follow-
ing characters up to a new-line to be ignored.
Aliasing
The first word of each command is replaced by the text of an
alias if an alias for this word has been defined. An alias
name consists of any number of characters excluding meta-
characters, quoting characters, file expansion characters,
parameter and command substitution characters, and =. The
replacement string can contain any valid shell script
including the metacharacters listed above. The first word
of each command in the replaced text, other than any that
are in the process of being replaced, will be tested for
aliases. If the last character of the alias value is a
blank then the word following the alias will also be checked
for alias substitution. Aliases can be used to redefine
special builtin commands but cannot be used to redefine the
reserved words listed above. Aliases can be created,
listed, and exported with the alias command and can be
removed with the unalias command. Exported aliases remain
in effect for scripts invoked by name, but must be reini-
tialized for separate invocations of the shell (see Invoca-
tion below). To prevent infinite loops in recursive alias-
ing, if the shell is not currently processing an alias of
the same name, the word will be replaced by the value of the
SunOS 5.5.1 Last change: 2 Jan 1996 4
ksh(1) User Commands ksh(1)
alias; otherwise, it will not be replaced.
Aliasing is performed when scripts are read, not while they
are executed. Therefore, for an alias to take effect the
alias definition command has to be executed before the com-
mand which references the alias is read.
Aliases are frequently used as a short hand for full path
names. An option to the aliasing facility allows the value
of the alias to be automatically set to the full pathname of
the corresponding command. These aliases are called tracked
aliases. The value of a tracked alias is defined the first
time the corresponding command is looked up and becomes
undefined each time the PATH variable is reset. These
aliases remain tracked so that the next subsequent reference
will redefine the value. Several tracked aliases are com-
piled into the shell. The -h option of the set command makes
each referenced command name into a tracked alias.
The following exported aliases are compiled into (and
built-in to) the shell but can be unset or redefined:
autoload='typeset -fu'
false='let 0'
functions='typeset -f'
hash='alias -t'
history='fc -l'
integer='typeset -i'
nohup='nohup '
r='fc -e -'
true=':'
type='whence -v'
An example concerning trailing blank characters and reserved
words follows. If the user types:
$ alias foo="/bin/ls "
$ alias while="/"
The effect of executing:
$ while true
> do
> echo "Hello, World"
> done
is a never-ending sequence of Hello, World strings to the
screen. However, if the user types:
$ foo while
the result will be an ls listing of /. Since the alias sub-
stitution for foo ends in a space character, the next word
SunOS 5.5.1 Last change: 2 Jan 1996 5
ksh(1) User Commands ksh(1)
is checked for alias substitution. The next word, while,
has also been aliased, so it is substituted as well. Since
it is not in the proper position as a command word, it is
not recognized as a reserved word.
If the user types:
$ foo; while
while retains its normal reserved-word properties.
Tilde Substitution
After alias substitution is performed, each word is checked
to see if it begins with an unquoted ~. If it does, then
the word up to a / is checked to see if it matches a user
name. If a match is found, the ~ and the matched login name
are replaced by the login directory of the matched user.
This is called a tilde substitution. If no match is found,
the original text is left unchanged. A ~ by itself, or in
front of a /, is replaced by $HOME. A ~ followed by a + or
- is replaced by $PWD and $OLDPWD respectively.
In addition, tilde substitution is attempted when the value
of a variable assignment begins with a ~.
Tilde Expansion
A tilde-prefix consists of an unquoted tilde character at
the beginning of a word, followed by all of the characters
preceding the first unquoted slash in the word, or all the
characters in the word if there is no slash. In an assign-
ment, multiple tilde-prefixes can be used: at the beginning
of the word (that is, following the equal sign of the
assignment), following any unquoted colon or both. A
tilde-prefix in an assignment is terminated by the first
unquoted colon or slash. If none of the characters in the
tilde-prefix are quoted, the characters in the tilde-prefix
following the tilde are treated as a possible login name
from the user database.
A portable login name cannot contain characters outside the
set given in the description of the LOGNAME environment
variable. If the login name is null (that is, the tilde-
prefix contains only the tilde), the tilde-prefix will be
replaced by the value of the variable HOME. If HOME is
unset, the results are unspecified. Otherwise, the tilde-
prefix will be replaced by a pathname of the home directory
associated with the login name obtained using the getpwnam
function. If the system does not recognize the login name,
the results are undefined.
Tilde expansion generally occurs only at the beginning of
words, but an exception based on historical practice has
SunOS 5.5.1 Last change: 2 Jan 1996 6
ksh(1) User Commands ksh(1)
been included:
PATH=/posix/bin:~dgk/bin
is eligible for tilde expansion because tilde follows a
colon and none of the relevant characters is quoted. Con-
sideration was given to prohibiting this behavior because
any of the following are reasonable substitutes:
PATH=$(printf %s ~karels/bin : ~bostic/bin)
for Dir in ~maart/bin ~srb/bin ...
do
PATH=${PATH:+$PATH:}$Dir
done
With the first command, explicit colons are used for each
directory. In all cases, the shell performs tilde expansion
on each directory because all are separate words to the
shell.
Note that expressions in operands such as:
make -k mumble LIBDIR=~chet/lib
do not qualify as shell variable assignments and tilde
expansion is not performed (unless the command does so
itself, which make does not).
The special sequence $~ has been designated for future
implementations to evaluate as a means of forcing tilde
expansion in any word.
Because of the requirement that the word not be quoted, the
following are not equivalent; only the last will cause tilde
expansion:
\~hlj/ ~h\lj/ ~"hlj"/ ~hlj\/ ~hlj/
The results of giving tilde with an unknown login name are
undefined because the KornShell ~+ and ~- constructs make
use of this condition, but, in general it is an error to
give an incorrect login name with tilde. The results of
having HOME unset are unspecified because some historical
shells treat this as an error.
Command Substitution
The standard output from a command enclosed in parenthesis
preceded by a dollar sign ( $(command) ) or a pair of grave
accents (``) may be used as part or all of a word; trailing
new-lines are removed. In the second (archaic) form, the
string between the quotes is processed for special quoting
characters before the command is executed. (See Quoting
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below.) The command substitution $(cat file) can be replaced
by the equivalent but faster (<file). Command substitution
of most special commands that do not perform input/output
redirection are carried out without creating a separate pro-
cess.
Command substitution allows the output of a command to be
substituted in place of the command name itself. Command
substitution occurs when the command is enclosed as follows:
$(command)
or (backquoted version):
`command`
The shell will expand the command substitution by executing
command in a subshell environment and replacing the command
substitution (the text of command plus the enclosing $( ) or
backquotes) with the standard output of the command, remov-
ing sequences of one or more newline characters at the end
of the substitution. Embedded newline characters before the
end of the output will not be removed; however, they may be
treated as field delimiters and eliminated during field
splitting, depending on the value of IFS and quoting that is
in effect.
Within the backquoted style of command substitution,
backslash shall retain its literal meaning, except when fol-
lowed by:
$ ` \
(dollar-sign, backquote, backslash). The search for the
matching backquote is satisfied by the first backquote found
without a preceding backslash; during this search, if a
non-escaped backquote is encountered within a shell comment,
a here-document, an embedded command substitution of the
$(command) form, or a quoted string, undefined results
occur. A single- or double-quoted string that begins, but
does not end, within the `...` sequence produces undefined
results.
With the $(command) form, all characters following the open
parenthesis to the matching closing parenthesis constitute
the command. Any valid shell script can be used for com-
mand, except:
o A script consisting solely of redirections produces
unspecified results.
o See the restriction on single subshells described below.
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The results of command substitution will not be field split-
ting and pathname expansion processed for further tilde
expansion, parameter expansion, command substitution or
arithmetic expansion. If a command substitution occurs
inside double-quotes, it will not be performed on the
results of the substitution.
Command substitution can be nested. To specify nesting
within the backquoted version, the application must precede
the inner backquotes with backslashes; for example:
`\`command\``
The $( ) form of command substitution solves a problem of
inconsistent behavior when using backquotes. For example:
Command Output
___________________________
echo '\$x' \$x
echo `echo '\$x'` $x
echo $(echo '\$x') \$x
Additionally, the backquoted syntax has historical restric-
tions on the contents of the embedded command. While the
new $( ) form can process any kind of valid embedded script,
the backquoted form cannot handle some valid scripts that
include backquotes. For example, these otherwise valid
embedded scripts do not work in the left column, but do work
on the right:
echo ` echo $(
cat <<eeof cat <<eeof
a here-doc with ` a here-doc with )
eof eof
` )
echo ` echo $(
echo abc # a comment with ` echo abc # a comment with )
` )
echo ` echo $(
echo '`' echo ')'
` )
Because of these inconsistent behaviors, the backquoted
variety of command substitution is not recommended for new
applications that nest command substitutions or attempt to
embed complex scripts.
If the command substitution consists of a single subshell,
such as:
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$( (command) )
a portable application must separate the $( and ( into two
tokens (that is, separate them with white space). This is
required to avoid any ambiguities with arithmetic expansion.
Arithmetic Expansion
An arithmetic expression enclosed in double parentheses pre-
ceded by a dollar sign ( $((arithmetic-expression)) ) is
replaced by the value of the arithmetic expression within
the double parenthesis. Arithmetic expansion provides a
mechanism for evaluating an arithmetic expression and sub-
stituting its value. The format for arithmetic expansion is
as follows:
$((expression))
The expression is treated as if it were in double-quotes,
except that a double-quote inside the expression is not
treated specially. The shell will expand all tokens in the
expression for parameter expansion, command substitution and
quote removal.
Next, the shell will treat this as an arithmetic expression
and substitute the value of the expression. The arithmetic
expression will be processed according to the rules of the
ISO C with the following exceptions:
o Only integer arithmetic is required.
o The sizeof() operator and the prefix and postfix ++
and -- operators are not required.
o Selection, iteration and jump statements are not sup-
ported.
As an extension, the shell may recognize arithmetic expres-
sions beyond those listed. If the expression is invalid,
the expansion will fail and the shell will write a message
to standard error indicating the failure.
A simple example using arithmetic expansion:
# repeat a command 100 times
x=100
while [ $x -gt 0 ]
do
command
x=$(($x-1))
done
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Process Substitution
This feature is available in SunOS and only on versions of
the UNIX operating system that support the /dev/fd directory
for naming open files. Each command argument of the form
<(list) or >(list) will run process list asynchronously con-
nected to some file in /dev/fd. The name of this file will
become the argument to the command. If the form with > is
selected then writing on this file will provide input for
list. If < is used, then the file passed as an argument
will contain the output of the list process. For example,
paste <(cut -f1 file1) <(cut -f3 file2) |
tee >( process1) >( process2)
cuts fields 1 and 3 from the files file1 and file2 respec-
tively, pastes the results together, and sends it to the
processes process1 and process2, as well as putting it onto
the standard output. Note that the file, which is passed as
an argument to the command, is a UNIX pipe(2) so programs
that expect to lseek(2) on the file will not work.
Parameter Substitution
A parameter is an identifier, one or more digits, or any of
the characters * , @, #, ?, -, $, and !. A variable (a
parameter denoted by an identifier) has a value and zero or
more attributes. variables can be assigned values and
attributes by using the typeset special command. The attri-
butes supported by the shell are described later with the
typeset special command. Exported variables pass values and
attributes to the environment.
The shell supports a one-dimensional array facility. An
element of an array variable is referenced by a subscript.
A subscript is denoted by a [, followed by an arithmetic
expression (see Arithmetic Evaluation below) followed by a
]. To assign values to an array, use set -A name value ....
The value of all subscripts must be in the range of 0
through 1023. Arrays need not be declared. Any reference
to a variable with a valid subscript is legal and an array
will be created if necessary. Referencing an array without
a subscript is equivalent to referencing the element 0. If
an array identifier with subscript * or @ is used, then the
value for each of the elements is substituted (separated by
a field separator character).
The value of a variable may be assigned by writing:
name=value [ name=value ] ...
If the integer attribute, -i, is set for name, the value is
subject to arithmetic evaluation as described below.
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Positional parameters, parameters denoted by a number, may
be assigned values with the set special command. Parameter
$0 is set from argument zero when the shell is invoked. If
parameter is one or more digits then it is a positional
parameter. A positional parameter of more than one digit
must be enclosed in braces.
Parameter Expansion
The format for parameter expansion is as follows:
${expression}
where expression consists of all characters until the match-
ing }. Any } escaped by a backslash or within a quoted
string, and characters in embedded arithmetic expansions,
command substitutions and variable expansions, are not exam-
ined in determining the matching }.
The simplest form for parameter expansion is:
${parameter}
The value, if any, of parameter will be substituted.
The parameter name or symbol can be enclosed in braces,
which are optional except for positional parameters with
more than one digit or when parameter is followed by a char-
acter that could be interpreted as part of the name. The
matching closing brace will be determined by counting brace
levels, skipping over enclosed quoted strings and command
substitutions.
If the parameter name or symbol is not enclosed in braces,
the expansion will use the longest valid name whether or not
the symbol represented by that name exists. When the shell
is scanning its input to determine the boundaries of a name,
it is not bound by its knowledge of what names are already
defined. For example, if F is a defined shell variable, the
command:
echo $Fred
does not echo the value of $F followed by red; it selects
the longest possible valid name, Fred, which in this case
might be unset.
If a parameter expansion occurs inside double-quotes:
o Pathname expansion will not be performed on the
results of the expansion.
o Field splitting will not be performed on the results
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of the expansion, with the exception of @.
In addition, a parameter expansion can be modified by using
one of the following formats. In each case that a value of
word is needed (based on the state of parameter, as
described below), word will be subjected to tilde expansion,
parameter expansion, command substitution and arithmetic
expansion. If word is not needed, it will not be expanded.
The } character that delimits the following parameter expan-
sion modifications is determined as described previously in
this section and in dquote. (For example, ${foo-bar}xyz}
would result in the expansion of foo followed by the string
xyz} if foo is set, else the string barxyz}).
${parameter:-word} Use Default Values. If parameter is
unset or null, the expansion of word
will be substituted; otherwise, the
value of parameter will be substituted.
${parameter:=word} Assign Default Values. If parameter is
unset or null, the expansion of word
will be assigned to parameter. In all
cases, the final value of parameter will
be substituted. Only variables, not
positional parameters or special parame-
ters, can be assigned in this way.
${parameter:?[word]}
Indicate Error if Null or Unset. If
parameter is unset or null, the expan-
sion of word (or a message indicating it
is unset if word is omitted) will be
written to standard error and the shell
will exit with a non-zero exit status.
Otherwise, the value of parameter will
be substituted. An interactive shell
need not exit.
${parameter:+[word]}
Use Alternative Value. If parameter is
unset or null, null will be substituted;
otherwise, the expansion of word will be
substituted.
In the parameter expansions shown previously, use of the
colon in the format results in a test for a parameter that
is unset or null; omission of the colon results in a test
for a parameter that is only unset. The following table
summarizes the effect of the colon:
_________________________________________________________________
parameter parameter parameter
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set and not null set but null unset
_________________________________________________________________
substitute substitute substitute
${parameter:-word} parameter word word
substitute substitute substitute
${parameter-word} parameter null word
substitute assign assign
${parameter:=word} parameter word word
substitute substitute assign
${parameter=word} parameter parameter null
substitute error, error,
${parameter:?word} parameter exit exit
substitute substitute error,
${parameter?word} parameter null exit
substitute substitute substitute
${parameter:+word} word null null
substitute substitute substitute
${parameter+word} word word null
In all cases shown with "substitute", the expression is
replaced with the value shown. In all cases shown with
"assign" parameter is assigned that value, which also
replaces the expression.
${#parameter} String Length. The length in characters
of the value of parameter. If parameter
is * or @, then all the positional parame-
ters, starting with $1, are substituted
(separated by a field separator charac-
ter).
The following four varieties of parameter expansion provide
for substring processing. In each case, pattern matching
notation (see patmat), rather than regular expression nota-
tion, will be used to evaluate the patterns. If parameter
is * or @, then all the positional parameters, starting with
$1, are substituted (separated by a field separator charac-
ter). Enclosing the full parameter expansion string in
double-quotes will not cause the following four varieties of
pattern characters to be quoted, whereas quoting characters
within the braces will have this effect.
${parameter%word} Remove Smallest Suffix Pattern. The
word will be expanded to produce a
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pattern. The parameter expansion then
will result in parameter, with the smal-
lest portion of the suffix matched by
the pattern deleted.
${parameter%%word} Remove Largest Suffix Pattern. The word
will be expanded to produce a pattern.
The parameter expansion then will result
in parameter, with the largest portion
of the suffix matched by the pattern
deleted.
${parameter#word} Remove Smallest Prefix Pattern. The
word will be expanded to produce a pat-
tern. The parameter expansion then will
result in parameter, with the smallest
portion of the prefix matched by the
pattern deleted.
${parameter##word} Remove Largest Prefix Pattern. The word
will be expanded to produce a pattern.
The parameter expansion then will result
in parameter, with the largest portion
of the prefix matched by the pattern
deleted.
Examples:
${parameter:-word}
In this example, ls is executed only if x is null or
unset. (The $(ls) command substitution notation is
explained in Command Substitution above.)
${x:-$(ls)}
${parameter:=word}
unset X
echo ${X:=abc}
abc
${parameter:?word}
unset posix
echo ${posix:?}
sh: posix: parameter null or not set
${parameter:+word}
set a b c
echo ${3:+posix}
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posix
${#parameter}
HOME=/usr/posix
echo ${#HOME}
10
${parameter%word}
x=file.c
echo ${x%.c}.o
file.o
${parameter%%word}
x=posix/src/std
echo ${x%%/*}
posix
${parameter#word}
x=$HOME/src/cmd
echo ${x#$HOME}
/src/cmd
${parameter##word}
x=/one/two/three
echo ${x##*/}
three
Parameters Set by Shell
The following parameters are automatically set by the shell:
# The number of positional parameters in
decimal.
- Flags supplied to the shell on invocation or
by the set command.
? The decimal value returned by the last exe-
cuted command.
$ The process number of this shell.
_ Initially, the value of _ is an absolute
pathname of the shell or script being exe-
cuted as passed in the environment. Subse-
quently it is assigned the last argument of
the previous command. This parameter is not
set for commands which are asynchronous.
This parameter is also used to hold the name
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of the matching MAIL file when checking for
mail.
! The process number of the last background
command invoked.
ERRNO The value of errno as set by the most
recently failed system call. This value is
system dependent and is intended for debug-
ging purposes.
LINENO The line number of the current line within
the script or function being executed.
OLDPWD The previous working directory set by the cd
command.
OPTARG The value of the last option argument pro-
cessed by the getopts special command.
OPTIND The index of the last option argument pro-
cessed by the getopts special command.
PPID The process number of the parent of the
shell.
PWD The present working directory set by the cd
command.
RANDOM Each time this variable is referenced, a ran-
dom integer, uniformly distributed between 0
and 32767, is generated. The sequence of
random numbers can be initialized by assign-
ing a numeric value to RANDOM.
REPLY This variable is set by the select statement
and by the read special command when no argu-
ments are supplied.
SECONDS Each time this variable is referenced, the
number of seconds since shell invocation is
returned. If this variable is assigned a
value, then the value returned upon reference
will be the value that was assigned plus the
number of seconds since the assignment.
Variables Used by Shell
The following variables are used by the shell:
CDPATH The search path for the cd command.
COLUMNS If this variable is set, the value is used to
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define the width of the edit window for the
shell edit modes and for printing select
lists.
EDITOR If the value of this variable ends in emacs,
gmacs, or vi and the VISUAL variable is not
set, then the corresponding option (see the
set special command below) will be turned on.
ENV This variable, when the
shell is invoked, is
subjected to parameter expansion by the shell
and the resulting value is used as a pathname
of a file containing shell commands to exe-
cute in the current environment. The file
need not be executable. If the expanded
value of ENV is not an absolute pathname, the
results are unspecified. ENV will be ignored
if the user's real and effective user IDs or
real and effective group IDs are different.
This variable can be used to set aliases and
other items local to the invocation of a
shell. The file referred to by ENV differs
from $HOME/.profile in that .profile is typi-
cally executed at session startup, whereas
the ENV file is executed at the beginning of
each shell invocation. The ENV value is
interpreted in a manner similar to a dot
script, in that the commands are executed in
the current environment and the file needs to
be readable, but not executable. However,
unlike dot scripts, no PATH searching is per-
formed. This is used as a guard against Tro-
jan Horse security breaches.
FCEDIT The default editor name for the fc command.
FPATH The search path for function definitions. By
default the FPATH directories are searched
after the PATH variable. If an executable
file is found, then it is read and executed
in the current environment. FPATH is
searched before PATH when a function with the
-u attribute is referenced. The preset alias
autoload preset alias causes a function with
the -u attribute to be created.
IFS Internal field separators, normally space,
tab, and new-line that are used to separate
command words which result from command or
parameter substitution and for separating
words with the special command read. The
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first character of the IFS variable is used
to separate arguments for the $* substitution
(See Quoting below).
HISTFILE If this variable is set when the shell is
invoked, then the value is the pathname of
the file that will be used to store the com-
mand history. (See Command re-entry below.)
HISTSIZE If this variable is set when the shell is
invoked, then the number of previously
entered commands that are accessible by this
shell will be greater than or equal to this
number. The default is 128.
HOME The default argument (home directory) for the
cd command.
LC_ALL This variable provides a default value for
the LC_* variables.
LC_COLLATE
This variable determines the behavior of
range expressions, equivalence classes and
multi-character collating elements within
pattern matching.
LC_CTYPE Determines how the shell handles characters.
When LC_CTYPE is set to a valid value, the
shell can display and handle text and
filenames containing valid characters for
that locale. However, the shell is not mul-
tibyte (EUC) capable. In the "C" locale,
only ASCII characters are valid. If LC_CTYPE
(see environ(5)) is not set in the environ-
ment, the operational behavior of the shell
is determined by the value of the LANG
environment variable. If LC_ALL is set, its
contents are used to override both the LANG
and the other LC_* variables. If none of the
above variables is set in the environment,
the "C" (U.S. style) locale prevails.
LC_MESSAGES
This variable determines the language in
which messages should be written.
LANG Provide a default value for the internation-
alization variables that are unset or null.
If LANG is unset or null, the corresponding
value from the default "C" locale will be
used. If any of the internationalization
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variables contains an invalid setting, the
utility will behave as if none of the vari-
ables had been defined.
LINENO This variable is set by the shell to a
decimal number representing the current
sequential line number (numbered starting
with 1) within a script or function before it
executes each command. If the user unsets or
resets LINENO, the variable may lose its spe-
cial meaning for the life of the shell. If
the shell is not currently executing a script
or function, the value of LINENO is unspeci-
fied.
LINES If this variable is set, the value is used to
determine the column length for printing
select lists. Select lists will print verti-
cally until about two-thirds of LINES lines
are filled.
MAIL If this variable is set to the name of a mail
file and the MAILPATH variable is not set,
then the shell informs the user of arrival of
mail in the specified file.
MAILCHECK This variable specifies how often (in
seconds) the shell will check for changes in
the modification time of any of the files
specified by the MAILPATH or MAIL variables.
The default value is 600 seconds. When the
time has elapsed the shell will check before
issuing the next prompt.
MAILPATH A colon (:) separated list of file names.
If this variable is set, then the shell
informs the user of any modifications to the
specified files that have occurred within the
last MAILCHECK seconds. Each file name can
be followed by a ? and a message that will be
printed. The message will undergo parameter
substitution with the variable $_ defined as
the name of the file that has changed. The
default message is you have mail in $_.
NLSPATH Determine the location of message catalogues
for the processing of LC_MESSAGES.
PATH The search path for commands (see Execution
below). The user may not change PATH if exe-
cuting under rksh (except in .profile).
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PPID This variable is set by the shell to the
decimal process ID of the process that
invoked the shell. In a subshell, PPID will
be set to the same value as that of the
parent of the current shell. For example,
echo $PPID and (echo $PPID) would produce the
same value.
PS1 The value of this variable is expanded for
parameter substitution to define the primary
prompt string which by default is ``$ ''.
The character ! in the primary prompt string
is replaced by the command number (see Com-
mand Re-entry below). Two successive
occurrences of ! will produce a single ! when
the prompt string is printed.
PS2 Secondary prompt string, by default ``> ''.
PS3 Selection prompt string used within a select
loop, by default ``#? ''.
PS4 The value of this variable is expanded for
parameter substitution and precedes each line
of an execution trace. If omitted, the exe-
cution trace prompt is ``+ ''.
SHELL The pathname of the shell is kept in the
environment. At invocation, if the basename
of this variable is rsh, rksh, or krsh, then
the shell becomes restricted.
TMOUT If set to a value greater than zero, the
shell will terminate if a command is not
entered within the prescribed number of
seconds after issuing the PS1 prompt. (Note
that the shell can be compiled with a maximum
bound for this value which cannot be
exceeded.)
VISUAL If the value of this variable ends in emacs,
gmacs, or vi then the corresponding option
(see Special Command set below) will be
turned on.
The shell gives default values to PATH, PS1, PS2, PS3, PS4,
MAILCHECK, FCEDIT, TMOUT and IFS, while HOME, SHELL ENV and
MAIL are not set at all by the shell (although HOME is set
by login(1)). On some systems MAIL and SHELL are also set
by login.
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Blank Interpretation
After parameter and command substitution, the results of
substitutions are scanned for the field separator characters
(those found in IFS) and split into distinct arguments where
such characters are found. Explicit null arguments ( "" )
or ('') are retained. Implicit null arguments (those
resulting from parameters that have no values) are removed.
File Name Generation
Following substitution, each command word is scanned for the
characters * , ?, and [ unless the -f option has been set.
If one of these characters appears then the word is regarded
as a pattern. The word is replaced with lexicographically
sorted file names that match the pattern. If no file name
is found that matches the pattern, then the word is left
unchanged. When a pattern is used for file name generation,
the character period (.) at the start of a file name or
immediately following a /, as well as the character /
itself, must be matched explicitly. A file name beginning
with a period will not be matched with a pattern with the
period inside parentheses; that is
ls .@(r*)
would locate a file named .restore, but ls @(.r*) would not.
In other instances of pattern matching the / and . are not
treated specially.
* Matches any string, including the null string.
? Matches any single character.
[...]
Matches any one of the enclosed characters. A
pair of characters separated by - matches any
character lexically between the pair, inclusive.
If the first character following the opening "[ "
is a "! ", then any character not enclosed is
matched. A - can be included in the character set
by putting it as the first or last character.
A pattern-list is a list of one or more patterns separated
from each other with a |. Composite patterns can be formed
with one or more of the following:
?(pattern-list) Optionally matches any one of the
given patterns.
*(pattern-list) Matches zero or more occurrences of
the given patterns.
+(pattern-list) Matches one or more occurrences of the
given patterns.
@(pattern-list) Matches exactly one of the given pat-
terns.
!(pattern-list) Matches anything, except one of the
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given patterns.
Quoting
Each of the metacharacters listed above (See Definitions)
has a special meaning to the shell and causes termination of
a word unless quoted. A character may be quoted (that is,
made to stand for itself) by preceding it with a \. The
pair \NEWLINE is removed. All characters enclosed between a
pair of single quote marks ('') are quoted. A single quote
cannot appear within single quotes. Inside double quote
marks (""), parameter and command substitution occur and \
quotes the characters \, `, ", and $. The meaning of $* and
$@ is identical when not quoted or when used as a parameter
assignment value or as a file name. However, when used as a
command argument, $* is equivalent to ``$1d$2d...'', where d
is the first character of the IFS variable, whereas $@ is
equivalent to $1 $2 .... Inside grave quote marks (``), \
quotes the characters \, `, and $. If the grave quotes
occur within double quotes, then \ also quotes the character
".
The special meaning of reserved words or aliases can be
removed by quoting any character of the reserved word. The
recognition of function names or special command names
listed below cannot be altered by quoting them.
Arithmetic Evaluation
An ability to perform integer arithmetic is provided with
the special command let. Evaluations are performed using
long arithmetic. Constants are of the form [ base# ] n
where base is a decimal number between two and thirty-six
representing the arithmetic base and n is a number in that
base. If base is omitted then base 10 is used.
An arithmetic expression uses the same syntax, precedence,
and associativity of expression as the C language. All the
integral operators, other than ++, --, ?:, and , are sup-
ported. Variables can be referenced by name within an
arithmetic expression without using the parameter substitu-
tion syntax. When a variable is referenced, its value is
evaluated as an arithmetic expression.
An internal integer representation of a variable can be
specified with the -i option of the typeset special command.
Arithmetic evaluation is performed on the value of each
assignment to a variable with the -i attribute. If you do
not specify an arithmetic base, the first assignment to the
variable determines the arithmetic base. This base is used
when parameter substitution occurs.
Since many of the arithmetic operators require quoting, an
alternative form of the let command is provided. For any
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ksh(1) User Commands ksh(1)
command which begins with a ((, all the characters until a
matching )) are treated as a quoted expression. More pre-
cisely, ((...)) is equivalent to let "...".
Prompting
When used interactively, the shell prompts with the parame-
ter expanded value of PS1 before reading a command. If at
any time a new-line is typed and further input is needed to
complete a command, then the secondary prompt (that is, the
value of PS2) is issued.
Conditional Expressions
A conditional expression is used with the [[ compound com-
mand to test attributes of files and to compare strings.
Word splitting and file name generation are not performed on
the words between [[ and ]]. Each expression can be con-
structed from one or more of the following unary or binary
expressions:
-a file True, if file exists.
-b file True, if file exists and is a block
special file.
-c file True, if file exists and is a character
special file.
-d file True, if file exists and is a direc-
tory.
-e file True, if file exists.
-f file True, if file exists and is an ordinary
file.
-g file True, if file exists and is has its
setgid bit set.
-k file True, if file exists and is has its
sticky bit set.
-n string True, if length of string is non-zero.
-o option True, if option named option is on.
-p file True, if file exists and is a fifo spe-
cial file or a pipe.
-r file True, if file exists and is readable by
current process.
-s file True, if file exists and has size
greater than zero.
-t fildes True, if file descriptor number fildes
is open and associated with a terminal
device.
-u file True, if file exists and has its setuid
bit set.
-w file True, if file exists and is writable by
current process.
-x file True, if file exists and is executable
by current process. If file exists and
is a directory, then the current process
has permission to search in the
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directory.
-z string True, if length of string is zero.
-L file True, if file exists and is a symbolic
link.
-O file True, if file exists and is owned by
the effective user id of this process.
-G file True, if file exists and its group
matches the effective group id of this
process.
-S file True, if file exists and is a socket.
file1 -nt file2 True, if file1 exists and is newer than
file2.
file1 -ot file2 True, if file1 exists and is older than
file2.
file1 -ef file2 True, if file1 and file2 exist and
refer to the same file.
string True if the string string is not the
null string.
string = pattern True, if string matches pattern.
string != pattern True, if string does not match pattern.
string1 = string2 True if the strings string1 and string2
are identical.
string1 ! = string2 True if the strings string1 and string2
are not identical.
string1 < string2 True, if string1 comes before string2
based on ASCII value of their charac-
ters.
string1 > string2 True, if string1 comes after string2
based on ASCII value of their charac-
ters.
exp1 -eq exp2 True, if exp1 is equal to exp2.
exp1 -ne exp2 True, if exp1 is not equal to exp2.
exp1 -lt exp2 True, if exp1 is less than exp2.
exp1 -gt exp2 True, if exp1 is greater than exp2.
exp1 -le exp2 True, if exp1 is less than or equal to
exp2.
exp1 -ge exp2 True, if exp1 is greater than or equal
to exp2.
In each of the above expressions, if file is of the form
/dev/fd/n, where n is an integer, then the test is applied
to the open file whose descriptor number is n.
A compound expression can be constructed from these primi-
tives by using any of the following, listed in decreasing
order of precedence.
(expression) True, if expression is true.
Used to group expressions.
! expression True if expression is false.
expression1 && expression2 True, if expression1 and
expression2 are both true.
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expression1 || expression2 True, if either expression1
or expression2 is true.
Input/Output
Before a command is executed, its input and output may be
redirected using a special notation interpreted by the
shell. The following may appear anywhere in a simple-
command or may precede or follow a command and are not
passed on to the invoked command. Command and parameter
substitution occur before word or digit is used except as
noted below. File name generation occurs only if the pat-
tern matches a single file, and blank interpretation is not
performed.
<word Use file word as standard input (file
descriptor 0).
>word Use file word as standard output (file
descriptor 1). If the file does not exist
then it is created. If the file exists, and
the noclobber option is on, this causes an
error; otherwise, it is truncated to zero
length.
>|word Sames as >, except that it overrides the
noclobber option.
>>word Use file word as standard output. If the
file exists then output is appended to it (by
first seeking to the EOF); otherwise, the
file is created.
<>word Open file word for reading and writing as
standard input.
<< [-]word The shell input is read up to a line that is
the same as word, or to an EOF. No parameter
substitution, command substitution or file
name generation is performed on word. The
resulting document, called a here-document,
becomes the standard input. If any character
of word is quoted, then no interpretation is
placed upon the characters of the document;
otherwise, parameter and command substitution
occur, \NEWLINE is ignored, and \ must be
used to quote the characters \, $, `, and the
first character of word. If - is appended to
<<, then all leading tabs are stripped from
word and from the document.
<&digit The standard input is duplicated from file
descriptor digit (see dup(2)). Similarly for
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the standard output using >&digit.
<&- The standard input is closed. Similarly for
the standard output using >&-.
<&p The input from the co-process is moved to
standard input.
>&p The output to the co-process is moved to
standard output.
If one of the above is preceded by a digit, then the file
descriptor number referred to is that specified by the digit
(instead of the default 0 or 1). For example:
... 2>&1
means file descriptor 2 is to be opened for writing as a
duplicate of file descriptor 1.
The order in which redirections are specified is signifi-
cant. The shell evaluates each redirection in terms of the
(file descriptor, file) association at the time of evalua-
tion. For example:
... 1>fname 2>&1
first associates file descriptor 1 with file fname. It then
associates file descriptor 2 with the file associated with
file descriptor 1 (that is fname). If the order of redirec-
tions were reversed, file descriptor 2 would be associated
with the terminal (assuming file descriptor 1 had been) and
then file descriptor 1 would be associated with file fname.
If a command is followed by & and job control is not active,
then the default standard input for the command is the empty
file /dev/null. Otherwise, the environment for the execu-
tion of a command contains the file descriptors of the
invoking shell as modified by input/output specifications.
Environment
The environment (see environ(5)) is a list of name-value
pairs that is passed to an executed program in the same way
as a normal argument list. The names must be identifiers
and the values are character strings. The shell interacts
with the environment in several ways. On invocation, the
shell scans the environment and creates a variable for each
name found, giving it the corresponding value and marking it
export. Executed commands inherit the environment. If the
user modifies the values of these variables or creates new
ones, using the export or typeset -x commands they become
part of the environment. The environment seen by any
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executed command is thus composed of any name-value pairs
originally inherited by the shell, whose values may be modi-
fied by the current shell, plus any additions which must be
noted in export or typeset -x commands.
The environment for any simple-command or function may be
augmented by prefixing it with one or more variable assign-
ments. A variable assignment argument is a word of the form
identifier=value. Thus:
TERM=450 cmd args
and
(export TERM; TERM=450; cmd args)
are equivalent (as far as the above execution of cmd is con-
cerned except for special commands listed below that are
preceded with a dagger).
If the -k flag is set, all variable assignment arguments are
placed in the environment, even if they occur after the com-
mand name. The following first prints a=b c and then c:
echo a=b c
set -k
echo a=b c
This feature is intended for use with scripts written for
early versions of the shell and its use in new scripts is
strongly discouraged. It is likely to disappear someday.
Functions
The function reserved word, described in the Commands sec-
tion above, is used to define shell functions. Shell func-
tions are read in and stored internally. Alias names are
resolved when the function is read. Functions are executed
like commands with the arguments passed as positional param-
eters. (See Execution below.)
Functions execute in the same process as the caller and
share all files and present working directory with the
caller. Traps caught by the caller are reset to their
default action inside the function. A trap condition that
is not caught or ignored by the function causes the function
to terminate and the condition to be passed on to the
caller. A trap on EXIT set inside a function is executed
after the function completes in the environment of the
caller. Ordinarily, variables are shared between the cal-
ling program and the function. However, the typeset special
command used within a function defines local variables whose
scope includes the current function and all functions it
calls.
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The special command return is used to return from function
calls. Errors within functions return control to the
caller.
The names of all functions can be listed with typeset +f.
typeset -f lists all function names as well as the text of
all functions. typeset -f function-names lists the text of
the named functions only. Functions can be undefined with
the -f option of the unset special command.
Ordinarily, functions are unset when the shell executes a
shell script. The -xf option of the typeset command allows
a function to be exported to scripts that are executed
without a separate invocation of the shell. Functions that
need to be defined across separate invocations of the shell
should be specified in the ENV file with the -xf option of
typeset.
Function Definition Command
A function is a user-defined name that is used as a simple
command to call a compound command with new positional
parameters. A function is defined with a function defini-
tion command.
The format of a function definition command is as follows:
fname() compound-command[io-redirect ...]
The function is named fname; it must be a name. An imple-
mentation may allow other characters in a function name as
an extension. The implementation will maintain separate
name spaces for functions and variables.
The () in the function definition command consists of two
operators. Therefore, intermixing blank characters with the
fname, (, and ) is allowed, but unnecessary.
The argument compound-command represents a compound command.
When the function is declared, none of the expansions in
wordexp will be performed on the text in compound-command or
io-redirect; all expansions will be performed as normal each
time the function is called. Similarly, the optional io-
redirect redirections and any variable assignments within
compound-command will be performed during the execution of
the function itself, not the function definition.
When a function is executed, it will have the syntax-error
and variable-assignment properties described for the special
built-in utilities.
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The compound-command will be executed whenever the function
name is specified as the name of a simple command The
operands to the command temporarily will become the posi-
tional parameters during the execution of the compound-
command; the special parameter # will also be changed to
reflect the number of operands. The special parameter 0
will be unchanged. When the function completes, the values
of the positional parameters and the special parameter #
will be restored to the values they had before the function
was executed. If the special built-in return is executed in
the compound-command, the function will complete and execu-
tion will resume with the next command after the function
call.
An example of how a function definition can be used wherever
a simple command is allowed:
# If variable i is equal to "yes",
# define function foo to be ls -l
#
[ "$i" = yes ] && foo() {
ls -l
}
The exit status of a function definition will be 0 if the
function was declared successfully; otherwise, it will be
greater than zero. The exit status of a function invocation
will be the exit status of the last command executed by the
function.
Jobs
If the monitor option of the set command is turned on, an
interactive shell associates a job with each pipeline. It
keeps a table of current jobs, printed by the jobs command,
and assigns them small integer numbers. When a job is
started asynchronously with &, the shell prints a line which
looks like:
[1] 1234
indicating that the job, which was started asynchronously,
was job number 1 and had one (top-level) process, whose pro-
cess id was 1234.
If you are running a job and wish to do something else you
may hit the key ^Z (CTRL-Z) which sends a STOP signal to the
current job. The shell will then normally indicate that the
job has been `Stopped', and print another prompt. You can
then manipulate the state of this job, putting it in the
background with the bg command, or run some other commands
and then eventually bring the job back into the foreground
with the foreground command fg. A ^Z takes effect
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ksh(1) User Commands ksh(1)
immediately and is like an interrupt in that pending output
and unread input are discarded when it is typed.
A job being run in the background will stop if it tries to
read from the terminal. Background jobs are normally
allowed to produce output, but this can be disabled by giv-
ing the command If you set this tty option, then background
jobs will stop when they try to produce output like they do
when they try to read input.
There are several ways to refer to jobs in the shell. A job
can be referred to by the process id of any process of the
job or by one of the following:
%number The job with the given number.
%string Any job whose command line begins with
string.
%?string Any job whose command line contains string.
%% Current job.
%+ Equivalent to %%.
%- Previous job.
The shell learns immediately whenever a process changes
state. It normally informs you whenever a job becomes
blocked so that no further progress is possible, but only
just before it prints a prompt. This is done so that it
does not otherwise disturb your work.
When the monitor mode is on, each background job that com-
pletes triggers any trap set for CHLD.
When you try to leave the shell while jobs are running or
stopped, you will be warned that `You have stopped(running)
jobs.' You may use the jobs command to see what they are.
If you do this or immediately try to exit again, the shell
will not warn you a second time, and the stopped jobs will
be terminated. If you have nohup'ed jobs running when you
attempt to logout, you will be warned with the message
You have jobs running.
You will then need to logout a second time to actually
logout; however, your background jobs will continue to run.
Signals
The INT and QUIT signals for an invoked command are ignored
if the command is followed by & and the monitor option is
not active. Otherwise, signals have the values inherited by
the shell from its parent (but see also the trap special
command below).
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Execution
Each time a command is executed, the above substitutions are
carried out. If the command name matches one of the Special
Commands listed below, it is executed within the current
shell process. Next, the command name is checked to see if
it matches one of the user defined functions. If it does,
the positional parameters are saved and then reset to the
arguments of the function call. When the function completes
or issues a return, the positional parameter list is
restored and any trap set on EXIT within the function is
executed. The value of a function is the value of the last
command executed. A function is also executed in the
current shell process. If a command name is not a special
command or a user defined function, a process is created and
an attempt is made to execute the command via exec(2).
The shell variable PATH defines the search path for the
directory containing the command. Alternative directory
names are separated by a colon (:). The default path is
/bin:/usr/bin: (specifying /bin, /usr/bin, and the current
directory in that order). The current directory can be
specified by two or more adjacent colons, or by a colon at
the beginning or end of the path list. If the command name
contains a / then the search path is not used. Otherwise,
each directory in the path is searched for an executable
file. If the file has execute permission but is not a
directory or an a.out file, it is assumed to be a file con-
taining shell commands. A sub-shell is spawned to read it.
All non-exported aliases, functions, and variables are
removed in this case. A parenthesized command is executed
in a sub-shell without removing non-exported quantities.
Command Re-entry
The text of the last HISTSIZE (default 128) commands entered
from a terminal device is saved in a history file. The file
$HOME/.sh_history is used if the HISTFILE variable is not
set or if the file it names is not writable. A shell can
access the commands of all interactive shells which use the
same named HISTFILE. The special command fc is used to list
or edit a portion of this file. The portion of the file to
be edited or listed can be selected by number or by giving
the first character or characters of the command. A single
command or range of commands can be specified. If you do
not specify an editor program as an argument to fc then the
value of the variable FCEDIT is used. If FCEDIT is not
defined then /bin/ed is used. The edited command(s) is
printed and re-executed upon leaving the editor. The editor
name - is used to skip the editing phase and to re-execute
the command. In this case a substitution parameter of the
form old=new can be used to modify the command before execu-
tion. For example, if r is aliased to 'fc -e -' then typing
`r bad=good c' will re-execute the most recent command which
SunOS 5.5.1 Last change: 2 Jan 1996 32
ksh(1) User Commands ksh(1)
starts with the letter c, replacing the first occurrence of
the string bad with the string good.
In-line Editing Option
Normally, each command line entered from a terminal device
is simply typed followed by a new-line (RETURN or LINEFEED).
If either the emacs, gmacs, or vi option is active, the user
can edit the command line. To be in either of these edit
modes set the corresponding option. An editing option is
automatically selected each time the VISUAL or EDITOR vari-
able is assigned a value ending in either of these option
names.
The editing features require that the user's terminal accept
RETURN as carriage return without line feed and that a space
must overwrite the current character on the screen.
The editing modes implement a concept where the user is
looking through a window at the current line. The window
width is the value of COLUMNS if it is defined, otherwise
80. If the window width is too small to display the prompt
and leave at least 8 columns to enter input, the prompt is
truncated from the left. If the line is longer than the
window width minus two, a mark is displayed at the end of
the window to notify the user. As the cursor moves and
reaches the window boundaries the window will be centered
about the cursor. The mark is a > if the line extends on
the right side of the window, < if the line extends on the
left, and * if the line extends on both sides of the window.
The search commands in each edit mode provide access to the
history file. Only strings are matched, not patterns,
although a leading ^ in the string restricts the match to
begin at the first character in the line.
emacs Editing Mode
This mode is entered by enabling either the emacs or gmacs
option. The only difference between these two modes is the
way they handle ^T. To edit, the user moves the cursor to
the point needing correction and then inserts or deletes
characters or words as needed. All the editing commands are
control characters or escape sequences. The notation for
control characters is caret ( ^ ) followed by the character.
For example, ^F is the notation for control F. This is
entered by depressing `f' while holding down the CTRL (con-
trol) key. The SHIFT key is not depressed. (The notation
^? indicates the DEL (delete) key.)
The notation for escape sequences is M- followed by a char-
acter. For example, M-f (pronounced Meta f) is entered by
depressing ESC (ascii 033) followed by `f'. (M-F would be
the notation for ESC followed by SHIFT (capital) `F'.)
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All edit commands operate from any place on the line (not
just at the beginning). Neither the RETURN nor the LINEFEED
key is entered after edit commands except when noted.
^F Move cursor forward (right) one character.
M-f Move cursor forward one word. (The emacs
editor's idea of a word is a string of char-
acters consisting of only letters, digits and
underscores.)
^B Move cursor backward (left) one character.
M-b Move cursor backward one word.
^A Move cursor to start of line.
^E Move cursor to end of line.
^]char Move cursor forward to character char on
current line.
M-^]char Move cursor backward to character char on
current line.
^X^X Interchange the cursor and mark.
erase (User defined erase character as defined by
the stty(1) command, usually ^H or #.)
Delete previous character.
^D Delete current character.
M-d Delete current word.
M-^H (Meta-backspace) Delete previous word.
M-h Delete previous word.
M-^? (Meta-DEL) Delete previous word (if your
interrupt character is ^? (DEL, the default)
then this command will not work).
^T Transpose current character with next charac-
ter in emacs mode. Transpose two previous
characters in gmacs mode.
^C Capitalize current character.
M-c Capitalize current word.
M-l Change the current word to lower case.
^K Delete from the cursor to the end of the
line. If preceded by a numerical parameter
whose value is less than the current cursor
position, then delete from given position up
to the cursor. If preceded by a numerical
parameter whose value is greater than the
current cursor position, then delete from
cursor up to given cursor position.
^W Kill from the cursor to the mark.
M-p Push the region from the cursor to the mark
on the stack.
kill (User defined kill character as defined by
the stty(1) command, usually ^G or @.) Kill
the entire current line. If two kill charac-
ters are entered in succession, all kill
characters from then on cause a line feed
(useful when using paper terminals).
^Y Restore last item removed from line. (Yank
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ksh(1) User Commands ksh(1)
item back to the line.)
^L Line feed and print current line.
^@ (null character) Set mark.
M-space (Meta space) Set mark.
J (New line) Execute the current line.
M (Return) Execute the current line.
eof End-of-file character, normally ^D, is pro-
cessed as an End-of-file only if the current
line is null.
^P Fetch previous command. Each time ^P is
entered the previous command back in time is
accessed. Moves back one line when not on
the first line of a multi-line command.
M-< Fetch the least recent (oldest) history line.
M-> Fetch the most recent (youngest) history
line.
^N Fetch next command line. Each time ^N is
entered the next command line forward in time
is accessed.
^Rstring Reverse search history for a previous command
line containing string. If a parameter of
zero is given, the search is forward. string
is terminated by a RETURN or NEW LINE. If
string is preceded by a ^, the matched line
must begin with string. If string is omit-
ted, then the next command line containing
the most recent string is accessed. In this
case a parameter of zero reverses the direc-
tion of the search.
^O Operate. Execute the current line and fetch
the next line relative to current line from
the history file.
M-digits (Escape) Define numeric parameter, the digits
are taken as a parameter to the next command.
The commands that accept a parameter are ^F,
^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
M-^], M-_, M-b, M-c, M-d, M-f, M-h, M-l and
M-^H.
M-letter Soft-key. Your alias list is searched for an
alias by the name _letter and if an alias of
this name is defined, its value will be
inserted on the input queue. The letter must
not be one of the above meta-functions.
M-[letter Soft-key. Your alias list is searched for an
alias by the name __letter and if an alias of
this name is defined, its value will be
inserted on the input queue. The can be used
to program functions keys on many terminals.
M-. The last word of the previous command is
inserted on the line. If preceded by a
numeric parameter, the value of this parame-
ter determines which word to insert rather
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ksh(1) User Commands ksh(1)
than the last word.
M-_ Same as M-..
M-* An asterisk is appended to the end of the
word and a file name expansion is attempted.
M-ESC File name completion. Replaces the current
word with the longest common prefix of all
filenames matching the current word with an
asterisk appended. If the match is unique, a
/ is appended if the file is a directory and
a space is appended if the file is not a
directory.
M-= List files matching current word pattern if
an asterisk were appended.
^U Multiply parameter of next command by 4.
\ Escape next character. Editing characters,
the user's erase, kill and interrupt (nor-
mally ^?) characters may be entered in a
command line or in a search string if pre-
ceded by a \. The \ removes the next
character's editing features (if any).
^V Display version of the shell.
M-# Insert a # at the beginning of the line and
execute it. This causes a comment to be
inserted in the history file.
vi Editing Mode
There are two typing modes. Initially, when you enter a
command you are in the input mode. To edit, the user enters
control mode by typing ESC (033) and moves the cursor to the
point needing correction and then inserts or deletes charac-
ters or words as needed. Most control commands accept an
optional repeat count prior to the command.
When in vi mode on most systems, canonical processing is
initially enabled and the command will be echoed again if
the speed is 1200 baud or greater and it contains any con-
trol characters or less than one second has elapsed since
the prompt was printed. The ESC character terminates canon-
ical processing for the remainder of the command and the
user can then modify the command line. This scheme has the
advantages of canonical processing with the type-ahead echo-
ing of raw mode.
If the option viraw is also set, the terminal will always
have canonical processing disabled. This mode is implicit
for systems that do not support two alternate end of line
delimiters, and may be helpful for certain terminals.
Input Edit Commands
By default the editor is in input mode.
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ksh(1) User Commands ksh(1)
erase (User defined erase character as defined by
the stty(1) command, usually ^H or #.)
Delete previous character.
^W Delete the previous blank separated word.
^D Terminate the shell.
^V Escape next character. Editing characters
and the user's erase or kill characters may
be entered in a command line or in a search
string if preceded by a ^V. The ^V removes
the next character's editing features (if
any).
\ Escape the next erase or kill character.
Motion Edit Commands
These commands will move the cursor.
[count]l Cursor forward (right) one character.
[count]w Cursor forward one alpha-numeric word.
[count]W Cursor to the beginning of the next word that
follows a blank.
[count]e Cursor to end of word.
[count]E Cursor to end of the current blank delimited
word.
[count]h Cursor backward (left) one character.
[count]b Cursor backward one word.
[count]B Cursor to preceding blank separated word.
[count]| Cursor to column count.
[count]fc Find the next character c in the current
line.
[count]Fc Find the previous character c in the current
line.
[count]tc Equivalent to f followed by h.
[count]Tc Equivalent to F followed by l.
[count]; Repeats count times, the last single charac-
ter find command, f, F, t, or T.
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ksh(1) User Commands ksh(1)
[count], Reverses the last single character find com-
mand count times.
0 Cursor to start of line.
^ Cursor to first non-blank character in line.
$ Cursor to end of line.
% Moves to balancing (, ), {, }, [, or ]. If
cursor is not on one of the above characters,
the remainder of the line is searched for the
first occurrence of one of the above charac-
ters first.
Search Edit Commands
These commands access your command history.
[count]k Fetch previous command. Each time k is
entered the previous command back in time is
accessed.
[count]- Equivalent to k.
[count]j Fetch next command. Each time j is entered
the next command forward in time is accessed.
[count]+ Equivalent to j.
[count]G The command number count is fetched. The
default is the least recent history command.
/string Search backward through history for a previ-
ous command containing string. string is
terminated by a RETURN or NEWLINE. If string
is preceded by a ^, the matched line must
begin with string. If string is NULL, the
previous string will be used.
?string Same as / except that search will be in the
forward direction.
n Search for next match of the last pattern to
/ or ? commands.
N Search for next match of the last pattern to
/ or ?, but in reverse direction. Search
history for the string entered by the previ-
ous / command.
Text Modification Edit Commands
These commands will modify the line.
SunOS 5.5.1 Last change: 2 Jan 1996 38
ksh(1) User Commands ksh(1)
a Enter input mode and enter text after the
current character.
A Append text to the end of the line.
Equivalent to $a.
[count]cmotion
c[count]motion
Delete current character through the charac-
ter that motion would move the cursor to and
enter input mode. If motion is c, the entire
line will be deleted and input mode entered.
C Delete the current character through the end
of line and enter input mode. Equivalent to
c$.
[count]s Delete count characters and enter input mode.
S Equivalent to cc.
D Delete the current character through the end
of line. Equivalent to d$.
[count]dmotion
d[count]motion
Delete current character through the charac-
ter that motion would move to. If motion is
d, the entire line will be deleted.
i Enter input mode and insert text before the
current character.
I Insert text before the beginning of the line.
Equivalent to 0i.
[count]P Place the previous text modification before
the cursor.
[count]p Place the previous text modification after
the cursor.
R Enter input mode and replace characters on
the screen with characters you type overlay
fashion.
[count]rc Replace the count character(s) starting at
the current cursor position with c, and
advance the cursor.
[count]x Delete current character.
SunOS 5.5.1 Last change: 2 Jan 1996 39
ksh(1) User Commands ksh(1)
[count]X Delete preceding character.
[count]. Repeat the previous text modification com-
mand.
[count]~ Invert the case of the count character(s)
starting at the current cursor position and
advance the cursor.
[count]_ Causes the count word of the previous command
to be appended and input mode entered. The
last word is used if count is omitted.
* Causes an * to be appended to the current
word and file name generation attempted. If
no match is found, it rings the bell. Other-
wise, the word is replaced by the matching
pattern and input mode is entered.
\ Filename completion. Replaces the current
word with the longest common prefix of all
filenames matching the current word with an
asterisk appended. If the match is unique, a
/ is appended if the file is a directory and
a space is appended if the file is not a
directory.
Other Edit Commands
Miscellaneous commands.
[count]ymotion
y[count]motion
Yank current character through character that
motion would move the cursor to and puts them into
the delete buffer. The text and cursor are
unchanged.
Y Yanks from current position to end of line.
Equivalent to y$.
u Undo the last text modifying command.
U Undo all the text modifying commands performed on
the line.
[count]v
Returns the command fc -e ${VISUAL:-${EDITOR:-vi}}
count in the input buffer. If count is omitted,
then the current line is used.
^L Line feed and print current line. Has effect only
in control mode.
SunOS 5.5.1 Last change: 2 Jan 1996 40
ksh(1) User Commands ksh(1)
J (New line) Execute the current line, regardless of
mode.
M (Return) Execute the current line, regardless of
mode.
# If the first character of the command is a #, then
this command deletes this # and each # that fol-
lows a newline. Otherwise, sends the line after
inserting a # in front of each line in the com-
mand. Useful for causing the current line to be
inserted in the history as a comment and removing
comments from previous comment commands in the
history file.
= List the file names that match the current word if
an asterisk were app
ended it.
@letter
Your alias list is searched for an alias by the
name _letter and if an alias of this name is
defined, its value will be inserted on the input
queue for processing.
Special Commands
The following simple-commands are executed in the shell pro-
cess. Input/Output redirection is permitted. Unless other-
wise indicated, the output is written on file descriptor 1
and the exit status, when there is no syntax error, is 0.
Commands that are preceded by one or two * (asterisks) are
treated specially in the following ways:
1. Variable assignment lists preceding the command
remain in effect when the command completes.
2. I/O redirections are processed after variable
assignments.
3. Errors cause a script that contains them to abort.
4. Words, following a command preceded by ** that are
in the format of a variable assignment, are expanded
with the same rules as a variable assignment. This
means that tilde substitution is performed after the
= sign and word splitting and file name generation
are not performed.
* : [ arg ... ]
The command only expands parameters.
* . file [ arg ... ]
Read the complete file then execute the commands. The
commands are executed in the current shell environment.
The search path specified by PATH is used to find the
directory containing file. If any arguments arg are
SunOS 5.5.1 Last change: 2 Jan 1996 41
ksh(1) User Commands ksh(1)
given, they become the positional parameters. Other-
wise the positional parameters are unchanged. The exit
status is the exit status of the last command executed.
** alias [ -tx ] [ name[ =value ] ] ...
alias with no arguments prints the list of aliases in
the form name=value on standard output. An alias is
defined for each name whose value is given. A trailing
space in value causes the next word to be checked for
alias substitution. The -t flag is used to set and
list tracked aliases. The value of a tracked alias is
the full pathname corresponding to the given name. The
value becomes undefined when the value of PATH is reset
but the aliases remained tracked. Without the -t flag,
for each name in the argument list for which no value
is given, the name and value of the alias is printed.
The -x flag is used to set or print exported aliases.
An exported alias is defined for scripts invoked by
name. The exit status is non-zero if a name is given,
but no value, and no alias has been defined for the
name.
bg [ %job... ]
This command is only on systems that support job con-
trol. Puts each specified job into the background.
The current job is put in the background if job is not
specified. See "Jobs" section above for a description
of the format of job.
* break [ n ]
Exit from the enclosed for, while, until, or select
loop, if any. If n is specified then break n levels.
* continue [ n ]
Resume the next iteration of the enclosed for, while,
until, or select loop. If n is specified then resume
at the n-th enclosed loop.
cd [ arg ]
cd old new
This command can be in either of two forms. In the
first form it changes the current directory to arg. If
arg is - the directory is changed to the previous
directory. The shell variable HOME is the default arg.
The variable PWD is set to the current directory. The
shell variable CDPATH defines the search path for the
directory containing arg. Alternative directory names
are separated by a colon (:). The default path is null
(specifying the current directory). Note that the
current directory is specified by a null path name,
which can appear immediately after the equal sign or
between the colon delimiters anywhere else in the path
SunOS 5.5.1 Last change: 2 Jan 1996 42
ksh(1) User Commands ksh(1)
list. If arg begins with a / then the search path is
not used. Otherwise, each directory in the path is
searched for arg.
The second form of cd substitutes the string new for
the string old in the current directory name, PWD and
tries to change to this new directory.
The cd command may not be executed by rksh.
command [-p] [command_name] [argument ...]
command [-v -V] command_name
The command utility causes the shell to treat the argu-
ments as a simple command, suppressing the shell func-
tion lookup. The -p flag performs the command search
using a default value for PATH that is guaranteed to
find all of the standard utilities. The -v flag writes
a string to standard output that indicates the pathname
or command that will be used by the shell, in the
current shell execution environment, to invoke
command_name. The -V flag writes a string to standard
output that indicates how the name given in the
command_name operand will be interpreted by the shell,
in the current shell execution environment.
* eval [ arg ... ]
The arguments are read as input to the shell and the
resulting command(s) executed.
* exec [ arg ... ]
If arg is given, the command specified by the arguments
is executed in place of this shell without creating a
new process. Input/output arguments may appear and
affect the current process. If no arguments are given
the effect of this command is to modify file descrip-
tors as prescribed by the input/output redirection
list. In this case, any file descriptor numbers
greater than 2 that are opened with this mechanism are
closed when invoking another program.
* exit [ n ]
Causes the calling shell or shell script to exit with
the exit status specified by n. The value will be the
least significant 8 bits of the specified status. If n
is omitted then the exit status is that of the last
command executed. When exit occurs when executing a
trap, the last command refers to the command that exe-
cuted before the trap was invoked. An EOF will also
cause the shell to exit except for a shell which has
the ignoreeof option (See set below) turned on.
** export [ name[=value] ] ...
The given names are marked for automatic export to the
SunOS 5.5.1 Last change: 2 Jan 1996 43
ksh(1) User Commands ksh(1)
environment of subsequently-executed commands.
fc [ -e ename ] [ -nlr ] [ first [ last ] ]
fc -e - [ old=new ] [ command ]
In the first form, a range of commands from first to
last is selected from the last HISTSIZE commands that
were typed at the terminal. The arguments first and
last may be specified as a number or as a string. A
string is used to locate the most recent command start-
ing with the given string. A negative number is used
as an offset to the current command number. If the - l
flag is selected, the commands are listed on standard
output. Otherwise, the editor program ename is invoked
on a file containing these keyboard commands. If ename
is not supplied, then the value of the variable FCEDIT
(default /bin/ed) is used as the editor. When editing
is complete, the edited command(s) is executed. If
last is not specified then it will be set to first. If
first is not specified the default is the previous com-
mand for editing and -16 for listing. The flag -r rev-
erses the order of the commands and the flag - n
suppresses command numbers when listing. In the second
form the command is re-executed after the substitution
old=new is performed. If there is not a command argu-
ment, the most recent command typed at this terminal is
executed.
fg [ %job... ]
This command is only on systems that support job con-
trol. Each job specified is brought to the foreground.
Otherwise, the current job is brought into the fore-
ground. See "Jobs" section above for a description of
the format of job.
getopts optstring name [ arg ... ]
Checks arg for legal options. If arg is omitted, the
positional parameters are used. An option argument
begins with a + or a -. An option not beginning with +
or - or the argument -- ends the options. optstring
contains the letters that getopts recognizes. If a
letter is followed by a :, that option is expected to
have an argument. The options can be separated from
the argument by blanks.
getopts places the next option letter it finds inside
variable name each time it is invoked with a +
prepended when arg begins with a +. The index of the
next arg is stored in OPTIND. The option argument, if
any, gets stored in OPTARG.
A leading : in optstring causes getopts to store the
letter of an invalid option in OPTARG, and to set name
SunOS 5.5.1 Last change: 2 Jan 1996 44
ksh(1) User Commands ksh(1)
to ? for an unknown option and to : when a required
option is missing. Otherwise, getopts prints an error
message. The exit status is non-zero when there are no
more options. See getoptcvt(1) for usage and descrip-
tion.
hash [ name ... ]
For each name, the location in the search path of the
command specified by name is determined and remembered
by the shell. The -r option causes the shell to forget
all remembered locations. If no arguments are given,
information about remembered commands is presented.
Hits is the number of times a command has been invoked
by the shell process. Cost is a measure of the work
required to locate a command in the search path. If a
command is found in a "relative" directory in the
search path, after changing to that directory, the
stored location of that command is recalculated. Com-
mands for which this will be done are indicated by an
asterisk (*) adjacent to the hits information. Cost
will be incremented when the recalculation is done.
jobs [ -lnp ] [ %job ... ]
Lists information about each given job; or all active
jobs if job is omitted. The -l flag lists process ids
in addition to the normal information. The -n flag
displays only jobs that have stopped or exited since
last notified. The -p flag causes only the process
group to be listed. See "Jobs" section above and
jobs(1) for a description of the format of job.
kill [ -sig ] %job ...
kill [ -sig ] pid ...
kill -l
Sends either the TERM (terminate) signal or the speci-
fied signal to the specified jobs or processes. Sig-
nals are either given by number or by names (as given
in signal(5) stripped of the prefix ``SIG'' with the
exception that SIGCHD is named CHLD). If the signal
being sent is TERM (terminate) or HUP (hangup), then
the job or process will be sent a CONT (continue) sig-
nal if it is stopped. The argument job can be the pro-
cess id of a process that is not a member of one of the
active jobs. See Jobs for a description of the format
of job. In the second form, kill -l, the signal
numbers and names are listed.
let arg...
Each arg is a separate arithmetic expression to be
evaluated. See the Arithmetic Evaluation section
above, for a description of arithmetic expression
evaluation.
SunOS 5.5.1 Last change: 2 Jan 1996 45
ksh(1) User Commands ksh(1)
The exit status is 0 if the value of the last expres-
sion is non-zero, and 1 otherwise.
login argument ...
Equivalent to `exec login argument....' See login(1)
for usage and description.
* newgrp [ arg ... ]
Equivalent to exec /bin/newgrp arg ....
print [ -Rnprsu[n ] ] [ arg ... ]
The shell output mechanism. With no flags or with flag
- or --, the arguments are printed on standard output
as described by echo(1). The exit status is 0, unless
the output file is not open for writing.
-n Suppress NEWLINE from being added to the
output.
-R | -r Raw mode. Ignore the escape conventions of
echo. The -R option will print all subse-
quent arguments and options other than -n.
-p Write the arguments to the pipe of the pro-
cess spawned with |& instead of standard out-
put.
-s Write the arguments to the history file
instead of standard output.
-u [ n ] Specify a one digit file descriptor unit
number n on which the output will be placed.
The default is 1.
pwd Equivalent to print -r - $PWD.
mechanism. One line is read and
read [ -
prsu[ n ] ] [ name?prompt ] [ name ... ] The shell input
is broken up into fields using the characters in IFS as
separators. The escape character, (\), is used to
remove any special meaning for the next character and
for line continuation. In raw mode, -r, the \ charac-
ter is not treated specially. The first field is
assigned to the first name, the second field to the
second name, etc., with leftover fields assigned to the
last name. The -p option causes the input line to be
taken from the input pipe of a process spawned by the
shell using |&. If the -s flag is present, the input
will be saved as a command in the history file. The
flag - u can be used to specify a one digit file
descriptor unit n to read from. The file descriptor
SunOS 5.5.1 Last change: 2 Jan 1996 46
ksh(1) User Commands ksh(1)
can be opened with the exec special command. The
default value of n is 0. If name is omitted then REPLY
is used as the default name. The exit status is 0
unless the input file is not open for reading or an EOF
is encountered. An EOF with the -p option causes
cleanup for this process so that another can be
spawned. If the first argument contains a ?, the
remainder of this word is used as a prompt on standard
error when the shell is interactive. The exit status
is 0 unless an EOF is encountered.
** readonly [ name[=value] ] ...
The given names are marked readonly and these names
cannot be changed by subsequent assignment.
* return [ n ]
Causes a shell function or '.' script to return to the
invoking script with the return status specified by n.
The value will be the least significant 8 bits of the
specified status. If n is omitted then the return
status is that of the last command executed. If return
is invoked while not in a function or a '.' script,
then it is the same as an exit.
set [ +-abCefhkmnopstuvx ] [ +-o option ]...
[ +-A name ] [ arg ... ]
The flags for this command have meaning as follows:
-A Array assignment. Unset the variable name and
assign values sequentially from the list arg. If
+A is used, the variable name is not unset first.
-a All subsequent variables that are defined are
automatically exported.
-b Causes the shell to notify the user asynchro-
nously of background job completions. The follow-
ing message will be written to standard error:
"[%d]%c %s%s\n", <job-number>, <current>,
<status>, <job-name>
where the fields are as follows:
<current> The character + identifies the job
that would be used as a default
for the fg or bg utilities; this
job can also be specified using
the job_id %+ or %%. The charac-
ter - identifies the job that
would become the default if the
current default job were to exit;
SunOS 5.5.1 Last change: 2 Jan 1996 47
ksh(1) User Commands ksh(1)
this job can also be specified
using the job_id %-. For other
jobs, this field is a space char-
acter. At most one job can be
identified with + and at most one
job can be identified with -. If
there is any suspended job, then
the current job will be a
suspended job. If there are at
least two suspended jobs, then the
previous job will also be a
suspended job.
<job-number> A number that can be used to iden-
tify the process group to the
wait, fg, bg, and kill utilities.
Using these utilities, the job can
be identified by prefixing the job
number with %.
<status> Unspecified.
<job-name> Unspecified.
When the shell notifies the user a job has been
completed, it may remove the job's process ID from
the list of those known in the current shell exe-
cution environment. Asynchronous notification
will not be enabled by default.
-C Prevent existing files from being overwritten by
the shell's > redirection operator; the >|
redirection operator will override this noclobber
option for an individual file.
-e If a command has a non-zero exit status, execute
the ERR trap, if set, and exit. This mode is dis-
abled while reading profiles.
-f Disables file name generation.
-h Each command becomes a tracked alias when first
encountered.
-k All variable assignment arguments are placed in
the environment for a command, not just those that
precede the command name.
-m Background jobs will run in a separate process
group and a line will print upon completion. The
exit status of background jobs is reported in a
completion message. On systems with job control,
SunOS 5.5.1 Last change: 2 Jan 1996 48
ksh(1) User Commands ksh(1)
this flag is turned on automatically for interac-
tive shells.
-n Read commands and check them for syntax errors,
but do not execute them. Ignored for interactive
shells.
-o The following argument can be one of the follow-
ing option names:
allexport Same as -a.
errexit Same as -e.
bgnice All background jobs are run at a lower
priority. This is the default mode.
emacs Puts you in an emacs style in-line
editor for command entry.
gmacs Puts you in a gmacs style in-line edi-
tor for command entry.
ignoreeof The shell will not exit on EOF. The
command exit must be used.
keyword Same as -k.
markdirs All directory names resulting from
file name generation have a trailing /
appended.
monitor Same as -m.
noclobber Prevents redirection > from truncating
existing files. Require >| to truncate
a file when turned on. Equivalent to
-C.
noexec Same as -n.
noglob Same as -f.
nolog Do not save function definitions in
history file.
notify Equivalent to -b.
nounset Same as -u.
privileged Same as -p.
verbose Same as -v.
trackall Same as -h.
vi Puts you in insert mode of a vi style
in-line editor until you hit escape
character 033. This puts you in con-
trol mode. A return sends the line.
viraw Each character is processed as it is
typed in vi mode.
xtrace Same as -x.
If no option name is supplied then the current
option settings are printed.
-p Disables processing of the $HOME/.profile file and
uses the file /etc/suid_profile instead of the ENV
file. This mode is on whenever the effective uid
is not equal to the real uid, or when the
SunOS 5.5.1 Last change: 2 Jan 1996 49
ksh(1) User Commands ksh(1)
effective gid is not equal to the real gid. Turn-
ing this off causes the effective uid and gid to
be set to the real uid and gid.
-s Sort the positional parameters lexicographically.
-t Exit after reading and executing one command.
-u Treat unset parameters as an error when substi-
tuting.
-v Print shell input lines as they are read.
-x Print commands and their arguments as they are
executed.
- Turns off -x and -v flags and stops examining
arguments for flags.
-- Do not change any of the flags; useful in set-
ting $1 to a value beginning with -. If no argu-
ments follow this flag then the positional parame-
ters are unset.
Using + rather than - causes these flags to be turned
off. These flags can also be used upon invocation of
the shell. The current set of flags may be found in $-
. Unless -A is specified, the remaining arguments are
positional parameters and are assigned, in order, to $1
$2 .... If no arguments are given then the names and
values of all variables are printed on the standard
output.
* shift [ n ]
The positional parameters from $n+1 $n+1 ... are
renamed $1 ..., default n is 1. The parameter n can be
any arithmetic expression that evaluates to a non-
negative number less than or equal to $#.
stop %jobid ...
stop pid ...
stop stops the execution of a background job(s) by
using its jobid, or of any process by using its pid.
(see ps(1)).
suspend
Stops the execution of the current shell (but not if it
is the login shell).
test expression
Evaluate conditional expressions. See Conditional
Expressions section above and test(1) for usage and
SunOS 5.5.1 Last change: 2 Jan 1996 50
ksh(1) User Commands ksh(1)
description.
* times
Print the accumulated user and system times for the
shell and for processes run from the shell.
* trap [ arg sig ... ]
arg is a command to be read and executed when the shell
receives signal(s) sig. arg is scanned once when the
trap is set and once when the trap is taken. sig can be
specified as a signal number or signal name. trap com-
mands are executed in order of signal number. Any
attempt to set a trap on a signal number that was
ignored on entry to the current shell is ineffective.
If arg is -, the shell will reset each sig to the
default value. If arg is null (''), the shell will
ignore each specified sig if it arises. Otherwise,
arg will be read and executed by the shell when one
of the corresponding sigs arises. The action of the
trap will override a previous action (either default
action or one explicitly set). The value of $? after
the trap action completes will be the value it had
before the trap was invoked.
sig can be EXIT, 0 (equivalent to EXIT) or a signal
specified using a symbolic name, without the SIG pre-
fix, for example, HUP, INT, QUIT, TERM. If sig is 0
or EXIT and the trap statement is executed inside the
body of a function, then the command arg is executed
after the function completes. If sig is 0 or EXIT for
a trap set outside any function then the command arg
is executed on exit from the shell. If sig is ERR
then arg will be executed whenever a command has a
non-zero exit status. If sig is DEBUG then arg will
be executed after each command.
The environment in which the shell executes a trap on
EXIT will be identical to the environment immediately
after the last command executed before the trap on
EXIT was taken.
Each time the trap is invoked, arg will be processed
in a manner equivalent to:
eval "$arg"
Signals that were ignored on entry to a non-
interactive shell cannot be trapped or reset,
although no error need be reported when attempting to
do so. An interactive shell may reset or catch sig-
nals ignored on entry. Traps will remain in place
SunOS 5.5.1 Last change: 2 Jan 1996 51
ksh(1) User Commands ksh(1)
for a given shell until explicitly changed with
another trap command.
When a subshell is entered, traps are set to the
default args. This does not imply that the trap com-
mand cannot be used within the subshell to set new
traps.
The trap command with no arguments will write to
standard output a list of commands associated with
each sig. The format is:
trap -- %s %s ... <arg>, <sig> ...
The shell will format the output, including the
proper use of quoting, so that it is suitable for
reinput to the shell as commands that achieve the
same trapping results. For example:
save_traps=$(trap)
...
eval "$save_traps"
If the trap name or number is invalid, a non-zero
exit status will be returned; otherwise, 0 will be
returned. For both interactive and non-interactive
shells, invalid signal names or numbers will not be
considered a syntax error and will not cause the
shell to abort.
Traps are not processed while a job is waiting for a
foreground process. Thus, a trap on CHLD won't be
executed until the foreground job terminates.
type name ...
For each name, indicate how it would be interpreted if
used as a command name.
** typeset [ +HLRZfilrtux[n] ] [ name[=value ] ] ...
Sets attributes and values for shell variables and
functions. When typeset is invoked inside a function,
a new instance of the variables name is created. The
variables value and type are restored when the function
completes. The following list of attributes may be
specified:
-H This flag provides UNIX to host-name file mapping
on non-UNIX machines.
-L Left justify and remove leading blanks from
value. If n is non-zero it defines the width of
the field; otherwise, it is determined by the
width of the value of first assignment. When the
variable is assigned to, it is filled on the right
with blanks or truncated, if necessary, to fit
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ksh(1) User Commands ksh(1)
into the field. Leading zeros are removed if the
-Z flag is also set. The -R flag is turned off.
-R Right justify and fill with leading blanks. If n
is non-zero it defines the width of the field,
otherwise it is determined by the width of the
value of first assignment. The field is left
filled with blanks or truncated from the end if
the variable is reassigned. The -L flag is turned
off.
-Z Right justify and fill with leading zeros if the
first non-blank character is a digit and the -L
flag has not been set. If n is non-zero it
defines the width of the field; otherwise, it is
determined by the width of the value of first
assignment.
-f The names refer to function names rather than
variable names. No assignments can be made and
the only other valid flags are -t, -u and -x. The
flag -t turns on execution tracing for this func-
tion. The flag -u causes this function to be
marked undefined. The FPATH variable will be
searched to find the function definition when the
function is referenced. The flag -x allows the
function definition to remain in effect across
shell procedures invoked by name.
-i Parameter is an integer. This makes arithmetic
faster. If n is non-zero it defines the output
arithmetic base; otherwise, the first assignment
determines the output base.
-l All upper-case characters are converted to lower-
case. The upper-case flag, -u is turned off.
-r The given names are marked readonly and these
names cannot be changed by subsequent assignment.
-t Tags the variables. Tags are user definable and
have no special meaning to the shell.
-u All lower-case characters are converted to upper-
case characters. The lower-case flag, -l is
turned off.
-x The given names are marked for automatic export
to the environment of subsequently-executed com-
mands.
The -i attribute can not be specified along with -R,
-L, -Z, or -f.
Using + rather than - causes these flags to be turned
off. If no name arguments are given but flags are
specified, a list of names (and optionally the values)
of the variables which have these flags set is printed.
(Using + rather than - keeps the values from being
printed.) If no names and flags are given, the names
and attributes of all variables are printed.
SunOS 5.5.1 Last change: 2 Jan 1996 53
ksh(1) User Commands ksh(1)
ulimit [ -HSacdfnstv ] [ limit ]
Set or display a resource limit. The available
resources limits are listed below. Many systems do not
contain one or more of these limits. The limit for a
specified resource is set when limit is specified. The
value of limit can be a number in the unit specified
below with each resource, or the value unlimited. The
H and S flags specify whether the hard limit or the
soft limit for the given resource is set. A hard limit
cannot be increased once it is set. A soft limit can
be increased up to the value of the hard limit. If
neither the H or S options is specified, the limit
applies to both. The current resource limit is printed
when limit is omitted. In this case the soft limit is
printed unless H is specified. When more that one
resource is specified, then the limit name and unit is
printed before the value.
-a Lists all of the current resource limits.
-c The number of 512-byte blocks on the size of core
dumps.
-d The number of K-bytes on the size of the data
area.
-f The number of 512-byte blocks on files written by
child processes (files of any size may be read).
-n The number of file descriptors plus 1.
-s The number of K-bytes on the size of the stack
area.
-t The number of seconds to be used by each process.
-v The number of K-bytes for virtual memory.
If no option is given, -f is assumed.
umask [-S] [ mask ]
The user file-creation mask is set to mask (see
umask(2)). mask can either be an octal number or a
symbolic value as described in chmod(1). If a symbolic
value is given, the new umask value is the complement
of the result of applying mask to the complement of the
previous umask value. If mask is omitted, the current
value of the mask is printed. The -S flag produces
symbolic output.
unalias name...
The aliases given by the list of names are removed from
the alias list.
unset [ -f ] name ...
The variables given by the list of names are unas-
signed, that is, their values and attributes are
erased. readonly variables cannot be unset. If the -
f, flag is set, then the names refer to function names.
Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND,
SunOS 5.5.1 Last change: 2 Jan 1996 54
ksh(1) User Commands ksh(1)
RANDOM, SECONDS, TMOUT, and _ removes their special
meaning even if they are subsequently assigned to.
* wait [ job ]
Wait for the specified job and report its termination
status. If job is not given then all currently active
child processes are waited for. The exit status from
this command is that of the process waited for. See
Jobs for a description of the format of job.
whence [ -pv ] name ...
For each name, indicate how it would be interpreted if
used as a command name.
The -v flag produces a more verbose report.
The -p flag does a path search for name even if name is
an alias, a function, or a reserved word.
Invocation
If the shell is invoked by exec(2), and the first character
of argument zero ($0) is -, then the shell is assumed to be
a login shell and commands are read from /etc/profile and
then from either .profile in the current directory or
$HOME/.profile, if either file exists. Next, commands are
read from the file named by performing parameter substitu-
tion on the value of the environment variable ENV if the
file exists. If the -s flag is not present and arg is, then
a path search is performed on the first arg to determine the
name of the script to execute. The script arg must have
read permission and any setuid and setgid settings will be
ignored. If the script is not found on the path, arg is
processed as if it named a builtin command or function.
Commands are then read as described below; the following
flags are interpreted by the shell when it is invoked:
-c string If the -c flag is present then commands are read
from string.
-s If the -s flag is present or if no arguments
remain then commands are read from the standard
input. Shell output, except for the output of the
Special Commands listed above, is written to file
descriptor 2.
-i If the -i flag is present or if the shell input
and output are attached to a terminal (as told by
ioctl(2)) then this shell is interactive. In this
case TERM is ignored (so that kill 0 does not kill
an interactive shell) and INTR is caught and
ignored (so that wait is interruptible). In all
cases, QUIT is ignored by the shell.
-r If the -r flag is present the shell is a res-
tricted shell.
SunOS 5.5.1 Last change: 2 Jan 1996 55
ksh(1) User Commands ksh(1)
The remaining flags and arguments are described under the
set command above.
rksh Only
rksh is used to set up login names and execution environ-
ments whose capabilities are more controlled than those of
the standard shell. The actions of rksh are identical to
those of ksh, except that the following are disallowed:
o changing directory (see cd(1))
o setting the value of SHELL, ENV, or PATH
o specifying path or command names containing /
o redirecting output (>, >|, <>, and >>)
o changing group (see newgrp(1)).
The restrictions above are enforced after .profile and the
ENV files are interpreted.
When a command to be executed is found to be a shell pro-
cedure, rksh invokes ksh to execute it. Thus, it is possi-
ble to provide to the end-user shell procedures that have
access to the full power of the standard shell, while impos-
ing a limited menu of commands; this scheme assumes that the
end-user does not have write and execute permissions in the
same directory.
The net effect of these rules is that the writer of the
.profile has complete control over user actions, by perform-
ing guaranteed setup actions and leaving the user in an
appropriate directory (probably not the login directory).
The system administrator often sets up a directory of com-
mands (that is, /usr/rbin) that can be safely invoked by
rksh.
ERRORS
Errors detected by the shell, such as syntax errors, cause
the shell to return a non-zero exit status. Otherwise, the
shell returns the exit status of the last command executed
(see also the exit command above). If the shell is being
used non-interactively then execution of the shell file is
abandoned. Run time errors detected by the shell are
reported by printing the command or function name and the
error condition. If the line number that the error occurred
on is greater than one, then the line number is also printed
in square brackets ([]) after the command or function name.
For a non-interactive shell, an error condition encountered
by a special built-in or other type of utility will cause
the shell to write a diagnostic message to standard error
and exit as shown in the following table:
SunOS 5.5.1 Last change: 2 Jan 1996 56
ksh(1) User Commands ksh(1)
________________________________________________________________
Error Special Built-in Other Utilities
________________________________________________________________
Shell language syntax error will exit will exit
Utility syntax error
(option or operand error) will exit will not exit
Redirection error will exit will not exit
Variable assignment error will exit will not exit
Expansion error will exit will exit
Command not found n/a may exit
Dot script not found will exit n/a
An expansion error is one that occurs when the shell expan-
sions are carried out (for example, ${x!y}, because ! is not
a valid operator); an implementation may treat these as syn-
tax errors if it is able to detect them during tokenization,
rather than during expansion.
If any of the errors shown as "will (may) exit" occur in a
subshell, the subshell will (may) exit with a non-zero
status, but the script containing the subshell will not exit
because of the error.
In all of the cases shown in the table, an interactive shell
will write a diagnostic message to standard error without
exiting.
EXIT STATUS
Each command has an exit status that can influence the
behavior of other shell commands. The exit status of com-
mands that are not utilities is documented in this section.
The exit status of the standard utilities is documented in
their respective sections.
If a command is not found, the exit status will be 127. If
the command name is found, but it is not an executable util-
ity, the exit status will be 126. Applications that invoke
utilities without using the shell should use these exit
status values to report similar errors.
If a command fails during word expansion or redirection, its
exit status will be greater than zero.
When reporting the exit status with the special parameter ?,
the shell will report the full eight bits of exit status
available. The exit status of a command that terminated
because it received a signal will be reported as greater
than 128.
FILES
/etc/profile
/etc/suid_profile
SunOS 5.5.1 Last change: 2 Jan 1996 57
ksh(1) User Commands ksh(1)
$HOME/.profile
/tmp/sh*
/dev/null
SEE ALSO
cat(1), cd(1), chmod(1), cut(1), echo(1), env(1),
getoptcvt(1), jobs(1), login(1), newgrp(1), paste(1), ps(1),
shell_builtins(1), stty(1), test(1), vi(1), dup(2), exec(2),
fork(2), ioctl(2), lseek(2), pipe(2), ulimit(2), umask(2),
wait(2), rand(3C), signal(3C), a.out(4), profile(4),
environ(5), signal(5)
Morris I. Bolsky and David G. Korn, The KornShell Command
and Programming Language, Prentice Hall, 1989.
WARNINGS
The use of setuid shell scripts is strongly discouraged.
NOTES
If a command which is a tracked alias is executed, and then
a command with the same name is installed in a directory in
the search path before the directory where the original com-
mand was found, the shell will continue to exec the original
command. Use the -t option of the alias command to correct
this situation.
Some very old shell scripts contain a ^ as a synonym for the
pipe character |.
Using the fc built-in command within a compound command will
cause the whole command to disappear from the history file.
The built-in command . file reads the whole file before any
commands are executed. Therefore, alias and unalias com-
mands in the file will not apply to any functions defined in
the file.
Please note:We(MWP)did NOT write these man files. The SunOS staff did.
We hope this helped with usage of UNIX commands.
EOF
