Each shell also includes built-in commands for efficiency. Table 16-6 lists the built-in commands. The Bourne shell relies more on using external commands to do the work, and thus has the fewest built-in commands. The additional built-in commands for the Korn shell are shown by (K) following the command name. The job control variant of the Bourne shell, jsh, has the same job control features as the Korn shell.
Table 16-6 Shell Built-In Commands
|
| Purpose
|
| Bourne or Korn Shell
| C Shell
|
| Null command
|
| :
| :
|
| Create a command name alias
|
| alias (K)
| alias
|
| Run current command in background
|
| bg (K)
| bg
|
| Exit enclosing for or while loop
|
| break
| break
|
| Break out of a switch
|
| N/A
| breaksw
|
| Change directory
|
| cd
| cd
|
| Continue next iteration of for or while loop
|
| continue
| continue
|
| Default case in switch
|
| N/A
| default
|
| Print directory stack
|
| N/A
| dirs
|
| Write arguments on stdout
|
| echo, print (K)
| echo
|
| Evaluate and execute arguments
|
| eval
| eval
|
| Execute the arguments
|
| exec
| exec
|
| Return or set shell variables
|
| N/A
| @
|
| Exit shell program
|
| exit
| exit
|
| Create an environment variable
|
| export
| setenv
|
| Bring a command into foreground
|
| fg (K)
| fg
|
| Execute foreach loop
|
| for
| foreach
|
| Perform filename expansion
|
| N/A
| glob
|
| Go to label within shell program
|
| N/A
| goto
|
| Display history list
|
| fc (K)
| history
|
| If-then-else decision
|
| if
| if
|
| List active jobs
|
| jobs (K)
| jobs
|
| Send a signal
|
| kill
| kill
|
| Set limits for a job's resource use
|
| ulimit
| limit
|
| Terminate login shell and invoke login
|
| N/A
| login
|
| Terminate a login shell
|
| N/A
| logout
|
| Change to a new user group
|
| newgrp (K)
| N/A
|
| Change priority of a command
|
| N/A
| nice
|
| Ignore hangup
|
| N/A
| nohup
|
| Notify user when job status changes
|
| N/A
| notify
|
| Control shell processing on receipt of a signal
|
| trap
| onintr
|
| Pop the directory stack
|
| N/A
| popd
|
| Push a directory onto the stack
|
| N/A
| pushd
|
| Read a line from stdin
|
| read
| $<
|
| Change a variable to read-only
|
| readonly
| N/A
|
| Repeat a command n times
|
| N/A
| repeat
|
| Set shell environment variables
|
| =
| setenv
|
| Set a local C shell variable
|
| N/A
| set
|
| Shift positional parameters $* or $argv
|
| shift
| shift
|
| Read and execute a file
|
| . (dot)
| source
|
| Stop a background process
|
| N/A
| stop
|
| Stop the shell
|
| suspend (K)
| suspend
|
| CASE statement
|
| case ... esac
| switch ... endsw
|
| Evaluate conditional expressions
|
| test
| N/A
|
| Display execution times
|
| times
| time
|
| Set default security for creation of files and directories
|
| umask
| umask
|
| Discard aliases
|
| unalias (K)
| unalias
|
| Remove limitations on resources
|
| ulimit
| unlimit
|
| Unset a variable
|
| unset
| unset
|
| Unset an environment variable
|
| N/A
| unsetenv
|
| UNTIL loop
|
| until
| N/A
|
| Wait for background process to complete
|
| wait
| N/A
|
| WHILE loop
|
| while
| while
|
|