SETENV(3) manual page
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setenv - change or add an environment
variable
#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
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 (and setenv() returns a success status). 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.
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.
- EINVAL
- name is
NULL, points to a string of length 0, or contains an aq=aq character.
- ENOMEM
- Insufficient memory to add a new variable to the environment.
4.3BSD, POSIX.1-2001.
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.
POSIX.1-2001 specifies that if name contains an
aq=aq character, then setenv() should fail with the error EINVAL; however,
versions of glibc before 2.3.4 allowed an aq=aq sign in name.
clearenv(3)
,
getenv(3)
, putenv(3)
, environ(7)
This page is part of release 3.78
of the Linux man-pages project. A description of the project, information
about reporting bugs, and the latest version of this page, can be found
at http://www.kernel.org/doc/man-pages/.
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