UNSETENV(3C) Standard C Library Functions UNSETENV(3C)
unsetenv - remove an environment variable
#include <stdlib.h>
int unsetenv(const char *name);
The unsetenv() function removes an environment variable from the
environment of the calling process. The name argument points to a
string that is the name of the variable to be removed. The named
argument cannot contain an '=' character. If the named variable does
not exist in the current environment, the environment is unchanged
and the function is considered to have completed successfully.
If the application modifies environ or the pointers to which it
points, the behavior of unsetenv() is undefined. The unsetenv()
function updates the list of pointers to which environ points.
Upon successful completion, 0 is returned. Otherwise, -1 is returned,
errno set to indicate the error, and the environment is left
unchanged.
The unsetenv() function will fail if:
EINVAL
The name argument is a null pointer, points to an empty
string, or points to a string containing an '=' character.
See attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
clearenv(3C), getenv(3C), setenv(3C), attributes(7), standards(7)
December 20, 2014 UNSETENV(3C)
NAME
unsetenv - remove an environment variable
SYNOPSIS
#include <stdlib.h>
int unsetenv(const char *name);
DESCRIPTION
The unsetenv() function removes an environment variable from the
environment of the calling process. The name argument points to a
string that is the name of the variable to be removed. The named
argument cannot contain an '=' character. If the named variable does
not exist in the current environment, the environment is unchanged
and the function is considered to have completed successfully.
If the application modifies environ or the pointers to which it
points, the behavior of unsetenv() is undefined. The unsetenv()
function updates the list of pointers to which environ points.
RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, -1 is returned,
errno set to indicate the error, and the environment is left
unchanged.
ERRORS
The unsetenv() function will fail if:
EINVAL
The name argument is a null pointer, points to an empty
string, or points to a string containing an '=' character.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
SEE ALSO
clearenv(3C), getenv(3C), setenv(3C), attributes(7), standards(7)
December 20, 2014 UNSETENV(3C)