putenv(3C)                     DG/UX 5.4R3.00                     putenv(3C)


NAME
       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.  The space used by
       string is no longer used once a new string-defining name is passed to
       putenv.  Because of this limitation, string should be declared static
       if it is declared within a function.


   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |              point    safe  |
                     +---------+-----------------------------+
                     |putenv   |     Y          N        N   |
                     +---------+-----------------------------+
       The environment information is global to all threads in a process.
       Changes to the environment occur immediately for all threads in a
       process.  putenv calls should be made when other threads will not be
       impacted by the call or can handle a change in the environment.

       Many of the shared library functions rely on the environment
       information in their processing. For instance, mktime relies on the
       timezone information in the environment in order to calculate its
       return value. If thread 1 issues a putenv call to change the timezone
       before thread 2 issues a mktime call, thread 2 will have results
       based on the the timezone thread 1 specified.


SEE ALSO
       exec(2), reentrant(3), getenv(3C), malloc(3C), environ(5).

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

NOTES
       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, environmental variables are not in
       alphabetical order.  A potential error is to call the function putenv



Licensed material--property of copyright holder(s)                         1

putenv(3C)                     DG/UX 5.4R3.00                     putenv(3C)


       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.






















































Licensed material--property of copyright holder(s)                         2