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:
Read-only variables with values cannot be reset.
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.
Export PWD and HOME variables:
export PWD HOME
Set and export the PATH variable:
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.
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .