|PUTENV(3)||Linux Programmer's Manual||PUTENV(3)|
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
- Insufficient space to allocate new environment.
|putenv ()||Thread safety||MT-Unsafe const:env|
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 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.
The GNU C library implementation provides a nonstandard extension. If string does not include an equal sign:
then the named variable is removed from the caller's environment.