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Name

shell_builtins - shell command interpreter built-in functions

Description

The shell command interpreters (sh(1) , csh(1) , and ksh(1) ), have special built-in functions which are interpreted by the shell as commands. Many of these built-in commands are implemented by more than one of the shells, and some are unique to a particular shell. These are:

commandbuilt into------------aliascsh, kshbgcsh, ksh, shbreakcsh, ksh, shcasecsh, ksh, shcdcsh, ksh, shchdircsh, shcontinuecsh, ksh, shdirscshechocsh, ksh, shevalcsh, ksh, shexeccsh, ksh, shexitcsh, ksh, shexportksh, shfckshfgcsh, ksh, shforksh, shforeachcshfunctionkshgetoptsksh, shglobcshgotocshhashksh, shhashstatcshhistorycshifcsh, ksh, shjobscsh, ksh, shkillcsh, ksh, shletkshlimitcshlogincsh, ksh, shlogoutcsh, ksh, shnicecshnewgrpksh, shnotifycshonintrcshpopdcshprintkshpushdcshpwdksh, shreadksh, shreadonlyksh, shrehashcshrepeatcshreturnksh, shselectkshsetcsh, ksh, shsetenvcshshiftcsh, ksh, shsourcecshstopcsh, ksh, shsuspendcsh, ksh, shswitchcshtestksh, shtimecshtimesksh, shtrapksh, shtypeksh, shtypesetkshulimitksh, shumaskcsh, ksh, shunaliascsh, kshunhashcshunlimitcshunsetcsh, ksh, shunsetenvcshuntilksh, shwaitcsh, ksh, shwhencekshwhilecsh, ksh, shBourne 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.

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

:
No effect; the command does nothing. A zero exit code is returned.
.
  • 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. Additional 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. .
    3. I/O redirections are processed after variable assignments.
    4. .
    5. Errors cause a script that contains them to abort.
    6. .
    7. 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.

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

    *

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

    *

    See Also

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


    Table of Contents