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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON |
SETENV(3) Linux Programmer's Manual SETENV(3)
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():
_POSIX_C_SOURCE >= 200112L
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
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
'=' character.
ENOMEM Insufficient memory to add a new variable to the environment.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────┬───────────────┬─────────────────────┐
│Interface │ Attribute │ Value │
├───────────┼───────────────┼─────────────────────┤
│setenv(), │ Thread safety │ MT-Unsafe const:env │
│unsetenv() │ │ │
└───────────┴───────────────┴─────────────────────┘
POSIX.1-2001, POSIX.1-2008, 4.3BSD.
POSIX.1 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-compliant prototype
shown in the SYNOPSIS.
POSIX.1 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.
clearenv(3), getenv(3), putenv(3), environ(7)
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latest version of this page, can be found at
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GNU 2016-03-15 SETENV(3)
Pages that refer to this page: clearenv(3), getenv(3), putenv(3), environ(7)