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

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(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)

Index

NAME

DESCRIPTION

Bourne Shell, sh, Special Commands

C shell, csh

Korn Shell, ksh, Special Commands

Korn Shell, ksh93, Special Commands

SEE ALSO

Партнёры:

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