Section: Linux Programmer's Manual (3)
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putenv - change or add an environment variable
int putenv(char *string);
Feature Test Macro Requirements for glibc (see
_SVID_SOURCE || _XOPEN_SOURCE
function adds or changes the value of environment
The argument string
is of the form name
does not already exist in the environment, then
is added to the environment.
then the value of name
in the environment is changed to
The string pointed to by string
becomes part of the environment,
so altering the string changes the environment.
function returns zero on success,
or nonzero if an error occurs.
In the event of an error,
is set to indicate the cause.
Insufficient space to allocate new environment.
SVr4, POSIX.1-2001, 4.3BSD.
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
In particular, this string becomes part of the environment;
changing it later will change the environment.
(Thus, it is an error is to call
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.
This page is part of release 3.74 of the Linux
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
- RETURN VALUE
- CONFORMING TO
- SEE ALSO