putenv(3)
Name
putenv − change or add value to environment
Syntax
int putenv (string)
char ∗string;
Description
The string points to a string of the form “name=value.” The putenv subroutine makes the value of the environment variable name equal to value by altering an existing variable or creating a new one. In either case, the string pointed to by string becomes part of the environment, so altering the string will change the environment. The space used by string is no longer used once a new string-defining name is passed to putenv.
Diagnostics
The putenv subroutine returns nonzero if it was unable to obtain enough space via malloc for an expanded environment, otherwise zero.
Warnings
The putenv subroutine manipulates the environment pointed to by environ, and can be used in conjunction with getenv. However, envp (the third argument to main) is not changed.
This routine uses malloc() to enlarge the environment.
After putenv is called, environmental variables are not in alphabetical order.
A potential error is to call putenv with an automatic variable as the argument, then exit the calling function while string is still part of the environment.