exit1p
Cause the shell to exit
Usage
exit [n]
Prolog
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
Overview
The exit utility shall cause the shell to exit from its current execution environment with the exit status specified by the unsigned decimal integer n. If the current execution environment is a subshell environment, the shell shall exit from the subshell environment with the specified exit status and continue in the environment from which that subshell environment was invoked; otherwise, the shell utility shall terminate with the specified exit status. If n is specified, but its value is not between 0 and 255 inclusively, the exit status is undefined.
A trap on EXIT shall be executed before the shell terminates, except when the exit utility is invoked in that trap itself, in which case the shell shall exit immediately.
Options
None.
Operands
See the DESCRIPTION.
Stdin
Not used.
Input files
None.
Environment
None.
Asynchronous events
Default.
Stdout
Not used.
Stderr
The standard error shall be used only for diagnostic messages.
Output files
None.
Extended description
None.
Exit status
The exit status shall be n, if specified, except that the behavior is unspecified if n is not an unsigned decimal integer or is greater than 255. Otherwise, the value shall be the exit value of the last command executed, or zero if no command was executed. When exit is executed in a trap action, the last command is considered to be the command that executed immediately preceding the trap action.
Consequences of errors
Default.
The following sections are informative.
Application usage
None.
Examples
Exit with a true value:
exit 0
Exit with a false value:
exit 1
Propagate error handling from within a subshell:
(
command1 || exit 1
command2 || exit 1
exec command3
) > outputfile || exit 1
echo "outputfile created successfully"
Rationale
As explained in other sections, certain exit status values have been reserved for special uses and should be used by applications only for those purposes:
126
|
A file to be executed was found, but it was not an executable utility. |
|---|---|
127
|
A utility to be executed was not found. |
>128
|
A command was interrupted by a signal. |
The behavior of exit when given an invalid argument or unknown option is unspecified, because of differing practices in the various historical implementations. A value larger than 255 might be truncated by the shell, and be unavailable even to a parent process that uses waitid() to get the full exit value. It is recommended that implementations that detect any usage error should cause a non-zero exit status (or, if the shell is interactive and the error does not cause the shell to abort, store a non-zero value in "$?"), but even this was not done historically in all shells.
Future directions
None.