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 IEEE Std 1003.1-2001, 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:
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1.
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Read-only variables with values cannot be reset.
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2.
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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.
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When no arguments are given, the results are unspecified.
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-fileunset 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.
