Manpage of PUTENV

PUTENV

Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Index
 

NAME

putenv - change or add an environment variable  

SYNOPSIS

#include <stdlib.h>int putenv(char *string);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

putenv(): _XOPEN_SOURCE
    || /* Glibc since 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _SVID_SOURCE  

DESCRIPTION

The putenv() function adds or changes the value of environment variables. The argument string is of the form name=value. If name does not already exist in the environment, then string is added to the environment. If name does exist, then the value of name in the environment is changed to value. The string pointed to by string becomes part of the environment, so altering the string changes the environment.  

RETURN VALUE

The putenv() function returns zero on success, or nonzero if an error occurs. In the event of an error, errnois set to indicate the cause.  

ERRORS

ENOMEM
Insufficient space to allocate new environment.
 

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
putenv() Thread safetyMT-Unsafe const:env
 

CONFORMING TO

POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.  

NOTES

The putenv() function is not required to be reentrant, and the one in glibc 2.0 is not, but the glibc 2.1 version is.

Since version 2.1.2, the glibc implementation conforms to SUSv2: the pointer string given to putenv() is used. In particular, this string becomes part of the environment; changing it later will change the environment. (Thus, it is an error is to call putenv() with an automatic variable as the argument, then return from the calling function while stringis still part of the environment.) However, glibc versions 2.0 to 2.1.1 differ: a copy of the string is used. On the one hand this causes a memory leak, and on the other hand it violates SUSv2.

The 4.4BSD version, like glibc 2.0, uses a copy.

SUSv2 removes the const from the prototype, and so does glibc 2.1.3.  

SEE ALSO

clearenv(3), getenv(3), setenv(3), unsetenv(3), environ(7)


 

Index

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

This document was created by man2html, using the manual pages.
Time: 16:30:24 GMT, October 09, 2016 Click Here!