putenv

Sets an environmental variable.

Format

#include  <stdlib.h>

int putenv  (const char *string);

Arguments

string
A pointer to a name=value string.

Description

This function sets the value of an environment variable by altering an existing variable or by creating a new one. The string argument points to a string of the form name=value, where name is the environment variable and value is the new value for it.

The string pointed to by string becomes part of the environment, so altering the string changes the environment. When a new string-defining name is passed to putenv, the space used by string is no longer used.


Note
The putenv function manipulates the environment pointed to by the environ external variable, and can be used with getenv. However, the third argument to the main function (the environment pointer), is not changed. The putenv function uses the malloc function to enlarge the environment. 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.

Return Values
Indicates success. 
-1  Indicates an error. errno is set to ENOMEM-Not enough memory available to expand the environment list. 

Restriction

This function cannot take a 64-bit address. See Section 1.8.


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