PUTENV (3)
change or add an environment variable
SYNOPSIS
#include <stdlib.h>
int putenv(const char * string );
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 -1 if an error
occurs.
ERRORS
ENOMEM
Insufficient space to allocate new environment.
NOTES
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 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.
However, glibc 2.0-2.1.1 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. 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 2.2.
CONFORMING TO
SEE ALSO
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