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) ; |
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 non-zero; 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)
Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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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 (faith@cs.unc.edu)
Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl)
Modified 9 Jun 2004, Michael Kerrisk <mtk-manpages@gmx.net>
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
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