putenv(3C)

putenv -- change or add value to environment

Synopsis

   #include <stdlib.h>
   
   int putenv (char string);

Description

string points to a string of the form ``name=value.'' putenv 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. string should not be a local (stack allocated) variable, since returning from the current function and calling a new one will change the environment. If name is later redefined by another putenv, string is no longer used. It may be altered or reused without affecting the environment.

Return values

putenv returns non-zero if it was unable to obtain enough space via malloc for an expanded environment, otherwise zero.

References

environ(5), exec(2), getenv(3C), malloc(3C)

Notices

putenv 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(3C) to enlarge the environment.

After putenv is called, environment variables are not in alphabetical order.

A potential error is to call the function putenv with a pointer to an automatic variable as the argument and to then exit the calling function while string is still part of the environment.