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PROGRAM:

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 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.1‐2008,
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. If a variable assignment
precedes the command name of export but that variable is not also listed as an operand of
export, then that variable shall be set in the current shell execution environment after
the completion of the export command, but it is unspecified whether that variable is
marked for export.

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

Zero.

CONSEQUENCES OF ERRORS

Default.

The following sections are informative.

APPLICATION USAGE

None.

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 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

None.

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