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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON |
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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.
setenv() and unsetenv() functions return 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)
This page is part of release 5.10 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
https://www.kernel.org/doc/man-pages/.
GNU 2017-09-15 SETENV(3)
Pages that refer to this page: ul(1), clearenv(3), getenv(3), pmgetconfig(3), putenv(3), environ(7)
Copyright and license for this manual page
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