SHELL_BUILTINS(1) User Commands SHELL_BUILTINS(1)


NAME


shell_builtins, case, for, foreach, function, if, repeat, select, switch,
until, while - shell command interpreter built-in commands

DESCRIPTION


The shell command interpreters csh(1), ksh(1), ksh93(1), and sh(1) have
special built-in commands. The commands case, for, foreach, function, if,
repeat, select, switch, until, and while are commands in the syntax
recognized by the shells. They are described in the Commands section of
the manual pages of the respective shells. In ksh93(1), fc, hash, stop,
suspend, times, and type are aliases by default. In ksh93, the following
built-ins are bound to the /bin pathname by default and are invoked if
the pathname search encounters an executable command of that name in the
/bin or /usr/bin directory: cat, chown, getconf, head, mkdir, rmdir, tee,
uniq, and wc.


The remaining commands listed in the following table are built into the
shells for reasons such as efficiency or data sharing between command
invocations. They are described on their respective manual pages.


Command Shell
-----------------------------------
++**alias csh, ksh, ksh93
bg csh, ksh, ksh93, sh
+*break csh, ksh, ksh93, sh
builtin ksh93
case csh, ksh, ksh93, sh
cat ksh93
cd csh, ksh, ksh93, sh
chdir csh, sh
chown ksh93
command ksh93
+*continue csh, ksh, ksh93, sh
dirs csh
disown ksh93
echo csh, ksh, ksh93, sh
+*eval csh, ksh, ksh93, sh
+*exec csh, ksh, ksh93, sh
+*exit csh, ksh, ksh93, sh
++**export ksh, ksh93, sh
false ksh, ksh93
fc ksh, ksh93
fg csh, ksh, ksh93, sh
for ksh, ksh93, sh
foreach csh
function ksh, ksh93
getconf ksh93
getopts ksh, ksh93, sh
glob csh
goto csh
hash ksh, ksh93, sh
hashstat csh
head ksh93
hist ksh93
history csh
if csh, ksh, ksh93, sh
jobs csh, ksh, ksh93, sh
kill csh, ksh, ksh93, sh
let ksh, ksh93,
limit csh
login csh, ksh, ksh93, sh
logout csh
mkdir ksh93
nice csh
+*newgrp ksh, ksh93, sh
nohup csh
notify csh
onintr csh
popd csh
print ksh, ksh93
printf ksh93
pushd csh
pwd ksh, ksh93, sh
read ksh, ksh93, sh
++**readonly ksh, ksh93, sh
rehash csh
repeat csh
+*return ksh, ksh93, sh
select ksh, ksh93
+set csh, ksh, ksh93, sh
setenv csh
shift csh, ksh, ksh93, sh
sleep ksh93
source csh
stop csh, ksh, ksh93, sh
suspend csh, ksh, sh
switch csh
tee ksh93
test ksh, ksh93, sh
time csh
*times ksh, ksh93, sh
*+trap ksh, ksh93, sh
true ksh, ksh93
type ksh, ksh93, sh
++**typeset ksh, ksh93
ulimit ksh, ksh93, sh
umask csh, ksh, ksh93, sh
+unalias csh, ksh, ksh93
unhash csh
uniq ksh93
unlimit csh
+unset csh, ksh, ksh93, sh
unsetenv csh
until ksh, ksh93, sh
*wait csh, ksh, ksh93, sh
whence ksh, ksh93
while csh, ksh, ksh93, sh


Bourne Shell, sh, Special Commands
Input/output redirection is now permitted for these commands. File
descriptor 1 is the default output location. When Job Control is enabled,
additional Special Commands are added to the shell's environment.


In addition to these built-in reserved command words, sh also uses:

:
No effect; the command does nothing. A zero exit code is
returned.


.filename
Read and execute commands from filename and return. The
search path specified by PATH is used to find the
directory containing filename.


C shell, csh
Built-in commands are executed within the C shell. If a built-in command
occurs as any component of a pipeline except the last, it is executed in
a subshell. In addition to these built-in reserved command words, csh
also uses:

:
Null command. This command is interpreted, but performs no action.


Korn Shell, ksh, Special Commands
Input/Output redirection is permitted. Unless otherwise indicated, the
output is written on file descriptor 1 and the exit status, when there is
no syntax error, is zero.


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.


In addition to these built-in reserved command words, ksh also uses:

* : [ 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 specified, they become the
positional parameters. Otherwise, the
positional parameters are unchanged. The
exit status is the exit status of the last
command executed. the loop termination test.


Korn Shell, ksh93, Special Commands
Input/Output redirection is permitted. Unless otherwise indicated, the
output is written on file descriptor 1 and the exit status, when there is
no syntax error, is zero.


Except for :, true, false, echo, newgrp, and login, all built-in commands
accept -- to indicate end of options. They also interpret the option
--man as a request to display the manual page onto standard error and -?
as a help request which prints a usage message on standard error.


Commands that are preceded by one or two + 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. They are not valid function names.

5. 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 field splitting
and file name generation are not performed.


In addition to these built-in reserved command words, ksh93 also uses:

: [ arg ... ]
The command only expands parameters.


.name [ arg ... ]
If name is a function defined with the
function name reserved word syntax, the
function is executed in the current
environment (as if it had been defined with
the name() syntax.) Otherwise if name refers
to a file, the file is read in its entirety
and the commands are executed in the current
shell environment. The search path specified
by PATH is used to find the directory
containing the file. If any arguments arg are
specified, they become the positional
parameters while processing the . command and
the original positional parameters are
restored upon completion. Otherwise the
positional parameters are unchanged. The exit
status is the exit status of the last command
executed.


SEE ALSO


Intro(1), alias(1), break(1), builtin(1), cd(1), chmod(1), csh(1),
disown(1), echo(1), exec(1), exit(1), find(1), getoptcvt(1), getopts(1),
glob(1), hash(1), history(1), jobs(1), kill(1), ksh(1), ksh93(1), let(1),
limit(1), login(1), logout(1), newgrp(1), nice(1), nohup(1), print(1),
printf(1), pwd(1), read(1), readonly(1), set(1), sh(1), shift(1),
sleep(1), suspend(1), test(1), test(1B), time(1), times(1), trap(1),
typeset(1), umask(1), wait(1), chdir(2), chmod(2), creat(2), umask(2),
getopt(3C), profile(4), environ(5)


November 20, 2007 SHELL_BUILTINS(1)