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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR S | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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EXPORT(1P) POSIX Programmer's Manual EXPORT(1P)
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.
export — set the export attribute for variables
export name[=word]...
export -p
The shell shall give the export attribute to the variables
corresponding to the specified names, which shall cause them to be
in the environment of subsequently executed commands. If the name
of a variable is followed by =word, then the value of that
variable shall be set to word.
The export special built-in shall support the Base Definitions
volume of POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
When -p is specified, export shall write to the standard output
the names and values of all exported variables, in the following
format:
"export %s=%s\n", <name>, <value>
if name is set, and:
"export %s\n", <name>
if name is unset.
The shell shall format the output, including the proper use of
quoting, so that it is suitable for reinput to the shell as
commands that achieve the same exporting results, except:
1. Read-only variables with values cannot be reset.
2. Variables that were unset at the time they were output need
not be reset to the unset state if a value is assigned to the
variable between the time the state was saved and the time at
which the saved output is reinput to the shell.
When no arguments are given, the results are unspecified.
See the DESCRIPTION.
See the DESCRIPTION.
Not used.
None.
None.
Default.
See the DESCRIPTION.
The standard error shall be used only for diagnostic messages.
None.
None.
0 All name operands were successfully exported.
>0 At least one name could not be exported, or the -p option
was specified and an error occurred.
Default.
The following sections are informative.
Note that, unless X was previously marked readonly, the value of
"$?" after:
export X=$(false)
will be 0 (because export successfully set X to the empty string)
and that execution continues, even if set -e is in effect. In
order to detect command substitution failures, a user must
separate the assignment from the export, as in:
X=$(false)
export X
Export PWD and HOME variables:
export PWD HOME
Set and export the PATH variable:
export PATH=/local/bin:$PATH
Save and restore all exported variables:
export -p > temp-file
unset a lot of variables
... processing
. temp-file
Some historical shells use the no-argument case as the functional
equivalent of what is required here with -p. This feature was
left unspecified because it is not historical practice in all
shells, and some scripts may rely on the now-unspecified results
on their implementations. Attempts to specify the -p output as the
default case were unsuccessful in achieving consensus. The -p
option was added to allow portable access to the values that can
be saved and then later restored using; for example, a dot script.
None.
Section 2.14, Special Built-In Utilities
The Base Definitions volume of POSIX.1‐2017, Section 12.2, Utility
Syntax Guidelines
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 .
IEEE/The Open Group 2017 EXPORT(1P)
Pages that refer to this page: readonly(1p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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