Originální popis anglicky:
putenv - change or add an environment variable
Návod, kniha: Linux Programmer's Manual
#include <stdlib.h>
int putenv(char *string);
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 -1 if an error occurs.
- ENOMEM
- Insufficient space to allocate new environment.
The
putenv() function is not required to be reentrant, and the one in
libc4, libc5 and glibc2.0 is not, but the glibc2.1 version is.
Description for libc4, libc5, glibc: If the argument
string is of the
form
name, and does not contain an `=' 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
glibc2.1.2.
The BSD4.4 version, like glibc 2.0, uses a copy.
SUSv2 removes the `const' from the prototype, and so does glibc 2.1.3.
SVID 3, POSIX, BSD 4.3
clearenv(3),
getenv(3),
setenv(3),
unsetenv(3),
environ(5)
