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.
exit — cause the shell to exit
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.
The standard error shall be used only for diagnostic messages.
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.
The following sections are informative.
Exit with a true value:
Exit with a false value:
Propagate error handling from within a subshell:
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:
command1 || exit 1
command2 || exit 1
) > outputfile || exit 1
echo "outputfile created successfully"
- A file to be executed was found, but it was not an executable
- A utility to be executed was not found.
- 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.
Section 2.14, Special Built-In Utilities
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1-2017, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018
Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html .
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