trusty (3) putenv.3posix.gz

NAME

       putenv - change or add a value to an environment

SYNOPSIS

       #include <stdlib.h>

       int putenv(char *string);

DESCRIPTION

       The  putenv()  function  shall  use  the  string  argument to set environment variable values. The string
       argument should point to a string of the form " name= value ".  The  putenv()  function  shall  make  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 shall become part of the  environment,  so  altering
       the  string  shall  change  the environment. The space used by string is no longer used once a new string
       which defines name is passed to putenv().

       The putenv() function need not be reentrant. A function that is not  required  to  be  reentrant  is  not
       required to be thread-safe.

RETURN VALUE

       Upon  successful completion, putenv() shall return 0; otherwise, it shall return a non-zero value and set
       errno to indicate the error.

ERRORS

       The putenv() function may fail if:

       ENOMEM Insufficient memory was available.

       The following sections are informative.

EXAMPLES

   Changing the Value of an Environment Variable
       The following example changes the value of the HOME environment variable to the value /usr/home.

              #include <stdlib.h>
              ...
              static char *var = "HOME=/usr/home";
              int ret;

              ret = putenv(var);

APPLICATION USAGE

       The putenv() function manipulates the environment pointed to by environ, and can be used  in  conjunction
       with getenv().

       See exec() , for restrictions on changing the environment in multi-threaded applications.

       This routine may use malloc() to enlarge the environment.

       A  potential  error  is to call putenv() with an automatic variable as the argument, then return from the
       calling function while string is still part of the environment.

       The setenv() function is preferred over this function.

RATIONALE

       The standard developers noted that putenv() is the only function available  to  add  to  the  environment
       without permitting memory leaks.

FUTURE DIRECTIONS

       None.

SEE ALSO

       exec() , getenv() , malloc() , setenv() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .