export(1p) — Linux manual page

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

EXPORT(1P)              POSIX Programmer's Manual             EXPORT(1P)

PROLOG         top

       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         top

       export — set the export attribute for variables

SYNOPSIS         top

       export name[=word]...

       export -p

DESCRIPTION         top

       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.

OPTIONS         top

       See the DESCRIPTION.

OPERANDS         top

       See the DESCRIPTION.

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       None.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       See the DESCRIPTION.

STDERR S         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

        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.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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

EXAMPLES         top

       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

RATIONALE         top

       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.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Section 2.14, Special Built-In Utilities

       The Base Definitions volume of POSIX.1‐2017, Section 12.2,
       Utility Syntax Guidelines

COPYRIGHT         top

       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:https://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)

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