@node putenv, environment
@findex putenv
@subheading Syntax

@example
#include <stdlib.h>

int putenv(char *env);
@end example

@subheading Description

This function adds an entry to the program's environment.  The string
passed must be of the form @code{NAME}=@code{VALUE}.  Any existing value
for the environment variable is gone. 

@code{putenv} will copy the string passed to it, and will
automatically free any existing string already in the environment.
Keep this in mind if you alter the environment yourself.  The string
you pass is still your responsibility to free.  Note that most
implementations will not let you free the string you pass, resulting
in memory leaks.

@subheading Return Value

Zero on success, nonzero on failure;  @code{errno} will be set to the
relevant error code: currently only @code{ENOMEM} (insufficient memory)
is possible.

@subheading Portability

@port-note posix This function is new to the Posix 1003.1-200x draft
@portability !ansi, posix

@subheading Example

@example
putenv("SHELL=ksh.exe");
@end example