putenv(3C) Standard C Library Functions putenv(3C)NAMEputenv - change or add value to environment
SYNOPSIS
#include <stdlib.h>
int putenv(char *string);
DESCRIPTION
The putenv() function 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 string argument points to a string of the form name=value. The
space used by string is no longer used once a new string-defining name
is passed to putenv().
The putenv() function uses malloc(3C) to enlarge the environment.
After putenv() is called, environment variables are not in alphabetical
order.
RETURN VALUES
Upon successful completion, putenv() returns 0. Otherwise, it returns a
non-zero value and sets errno to indicate the error.
ERRORS
The putenv() function may fail if:
ENOMEM Insufficient memory was available.
USAGE
The putenv() function can be safely called from multithreaded programs.
Caution must be exercised when using this function and getenv(3C) in
multithreaded programs.
These functions examine and modify the environment list, which is
shared by all threads in a program. The system prevents the list from
being accessed simultaneously by two different threads. It does not,
however, prevent two threads from successively accessing the environ‐
ment list using putenv() or getenv().
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOexec(2), getenv(3C), malloc(3C), attributes(5), environ(5), stan‐
dards(5)WARNINGS
The string argument should not be an automatic variable. It should be
declared static if it is declared within a function because it cannot
be automatically declared. A potential error is to call 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.
SunOS 5.10 7 Aug 2004 putenv(3C)