EXPORT(1POSIX) POSIX Programmer's Manual EXPORT(1POSIX)
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NAME
export -- set the export attribute for variables
SYNOPSIS
export name[=word]...
export -p
DESCRIPTION
The shell shall give the export attribute to the variables correspond-
ing to the specified names, which shall cause them to be in the envi-
ronment 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 be-
tween 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
See the DESCRIPTION.
OPERANDS
See the DESCRIPTION.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
None.
ASYNCHRONOUS EVENTS
Default.
STDOUT
See the DESCRIPTION.
STDERR S
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
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
Default.
The following sections are informative.
APPLICATION USAGE
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 de-
tect command substitution failures, a user must separate the assignment
from the export, as in:
X=$(false)
export X
EXAMPLES
Export PWD and HOME variables:
export PWD HOME
Set and export the PATH variable:
export PATH=/local/bin:$PATH
Save and restore all exported variables:
export -p > temp-file
unset a lot of variables
... processing
. temp-file
RATIONALE
Some historical shells use the no-argument case as the functional
equivalent of what is required here with -p. This feature was left un-
specified because it is not historical practice in all shells, and some
scripts may rely on the now-unspecified results on their implementa-
tions. Attempts to specify the -p output as the default case were un-
successful 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
None.
SEE ALSO
Section 2.14, Special Built-In Utilities
The Base Definitions volume of POSIX.1-2017, Section 12.2, Utility Syn-
tax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology -- Por-
table Operating System Interface (POSIX), The Open Group Base Specifi-
cations 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.ker-
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IEEE/The Open Group 2017 EXPORT(1POSIX)
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