EXIT
Section: POSIX Programmer's Manual (1P)
Updated: 2017
Page Index
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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.
NAME
exit
--- cause the shell to exit
SYNOPSIS
exit [n]
DESCRIPTION
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 VARIABLES
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.
SEE ALSO
Section 2.14,
Special Built-In Utilities
COPYRIGHT
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 .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .