SETENV
Section: Linux Programmer's Manual (3)
Updated: 2009-09-20
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);
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.
This function makes copies of the strings pointed to by
name
and
value
(by contrast with
putenv(3)).
The
unsetenv()
function deletes the variable name from
the environment.
If
name
does not exist in the environment,
then the function succeeds, and the environment is unchanged.
RETURN VALUE
The
setenv()
function returns zero on success,
or -1 on error, with
errno
set to indicate the cause of the error.
The
unsetenv()
function returns zero on success,
or -1 on error, with
errno
set to indicate the cause of the error.
ERRORS
- EINVAL
-
name
is NULL, points to a string of length 0,
or contains an '=' character.
- ENOMEM
-
Insufficient memory to add a new variable to the environment.
CONFORMING TO
4.3BSD, POSIX.1-2001.
NOTES
POSIX.1-2001 does not require
setenv()
or
unsetenv()
to be reentrant.
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 3.27 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- BUGS
-
- SEE ALSO
-
- COLOPHON
-
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Time: 07:35:09 GMT, March 26, 2013