PUTENV(3) manual page
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putenv - change or add an environment
variable
#include <stdlib.h>
int putenv(char *string);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)
):
putenv(): _SVID_SOURCE || _XOPEN_SOURCE
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.
The putenv() function returns
zero on success, or nonzero if an error occurs. In the event of an error,
errno is set to indicate the cause.
- ENOMEM
- Insufficient space to allocate
new environment.
SVr4, POSIX.1-2001, 4.3BSD.
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 string
is 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.
clearenv(3)
, getenv(3)
, setenv(3)
, unsetenv(3)
, environ(7)
This page is part of release 3.78 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/.
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