NAME

putenv − change or add value to environment

SYNOPSIS

int putenv(string)
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.  The space used by string is no longer used once a new string-defining name is passed to putenv(). 

SEE ALSO

execve(2V), getenv(3V), malloc(3V), environ(5V). 

DIAGNOSTICS

putenv() returns non-zero if it was unable to obtain enough space using malloc(3V) for an expanded environment, otherwise zero. 

WARNINGS

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(3V) 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. 

Sun Release 4.1  —  Last change: 21 February 1989