[MAN] setenv

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SETENV

Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Index Return to Main Contents

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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():

_POSIX_C_SOURCE >= 200112L
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE

 

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 '=' 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.  

BUGS

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.  

SEE ALSO

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

COLOPHON

This page is part of release 4.15 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/.

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Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

NOTES

BUGS

SEE ALSO

COLOPHON

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