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SETENV

Section: Linux Programmer's Manual (3)
Updated: 2015-03-02
Index Return to Main Contents
 

NAME

setenv - change or add an environment variable  

SYNOPSIS

#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).
InterfaceAttributeValue
setenv(), unsetenv() Thread safetyMT-Unsafe const:env
 

CONFORMING TO

4.3BSD, POSIX.1-2001.  

NOTES

POSIX.1-2001 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.1-2001-compliant prototype shown in the SYNOPSIS.  

BUGS

POSIX.1-2001 specifies that if name contains an aq=aq character, then setenv() should fail with the error EINVAL; however, versions of glibc before 2.3.4 allowed an aq=aq sign in name.  

SEE ALSO

clearenv(3), getenv(3), putenv(3), environ(7)  

COLOPHON

This page is part of release 3.81 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 http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
NOTES
BUGS
SEE ALSO
COLOPHON


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