unsetenv (3)
Leading comments
Copyright 1993 David Metcalfe (david@prism.demon.co.uk) and Copyright (C) 2004, 2007 Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distribu...
NAME
setenv - change or add an environment variableSYNOPSIS
#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
DESCRIPTION
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
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.
ERRORS
- 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.
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 |
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.3BSD.NOTES
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.