from small one page howto to huge articles all in one place
poll results
Last additions:
May 25th. 2007:
April, 26th. 2006:
| You are here: manpages
PUTENV
Section: Linux Programmer's Manual (3)
Updated: 2007-07-26
Index
Return to Main Contents
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():
_SVID_SOURCE || _XOPEN_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.
ERRORS
- ENOMEM
-
Insufficient space to allocate new environment.
CONFORMING TO
SVr4, POSIX.1-2001, 4.3BSD.
NOTES
The
putenv()
function is not required to be reentrant, and the
one in libc4, libc5 and glibc 2.0 is not, but the glibc 2.1 version is.
Description for libc4, libc5, glibc:
If the argument string is of the form name,
and does not contain an aq=aq character, then the variable name
is removed from the environment.
If
putenv()
has to allocate a new array environ,
and the previous array was also allocated by
putenv(),
then it will be freed.
In no case will the old storage associated
to the environment variable itself be freed.
The libc4 and libc5 and glibc 2.1.2 versions conform 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 string
is still part of the environment.)
However, glibc 2.0-2.1.1 differs: a copy of the string is used.
On the one hand this causes a memory leak, and on the other hand
it violates SUSv2.
This has been fixed in glibc 2.1.2.
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)
COLOPHON
This page is part of release 3.27 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
Please read "Why adblockers are badwww.cars2fast4u.de
|
Other free services .
.
| 
|
|
- Running on 
-
:
: 
