unsetenv3
Change or add an environment variable
Part of setenv(3).
Usage
#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 <= 2.19: */ _BSD_SOURCE
Library
Standard C library (libc, -lc)
Overview
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.
Return value
setenv() and unsetenv() functions return zero on success, or -1 on error, with errno set to indicate 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. |
Attributes
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| setenv(), unsetenv() | Thread safety | MT-Unsafe const:env |
Caveats
POSIX.1 does not require setenv() or unsetenv() to be reentrant.
Releases
19 releases since Debian 1.1 (Buzz); the text changed 15 times.