Name

setenv — change or add an environment variable

Synopsis

#include <stdlib.h>
int setenv( const char *  name,
  const char *  value,
  int   overwrite);
int unsetenv( const char *  name);
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
setenv(), unsetenv():
_BSD_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600

DESCRIPTION

The setenv() function adds the variable name to the environment with the value value, if name does not already exist. If name does exist in the environment, then its value is changed to value if overwrite is nonzero; if overwrite is zero, then the value of name is not changed.

The unsetenv() function deletes the variable name from the environment.

RETURN VALUE

The setenv() function returns zero on success, or −1 if there was insufficient space in the environment. The unsetenv() function returns zero on success, or −1 on error, with errno set to indicate the cause of the error.

ERRORS

EINVAL

name contained an '=' character.

CONFORMING TO

4.3BSD, POSIX.1-2001.

NOTES

Prior to glibc 2.2.2, unsetenv() was prototyped as returning void; more recent glibc versions follow the POSIX.1-2001-compliant prototype shown in the SYNOPSIS.

BUGS

POSIX.1-2001 specifies that if name contains an '=' character, then setenv() should fail with the error EINVAL; however, versions of glibc before 2.3.4 allowed an '=' sign in name.

SEE ALSO

clearenv(3), getenv(3), putenv(3), environ(7)

COLOPHON

This page is part of release 2.79 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
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permission notice identical to this one.

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responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
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which is licensed free of charge, as they might when working
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Formatted or processed versions of this manual, if unaccompanied by
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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified Sat Jul 24 18:20:58 1993 by Rik Faith (faithcs.unc.edu)
Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aebcwi.nl)
Modified 9 Jun 2004, Michael Kerrisk <mtk.manpagesgmail.com>
    Changed unsetenv() prototype; added EINVAL error
    Noted non-standard behavior of setenv() if name contains '='
2005-08-12, mtk, glibc 2.3.4 fixed the "name contains '='" bug