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Linux 2.6 - man page for putenv (linux section 3posix)

PUTENV(P)			    POSIX Programmer's Manual				PUTENV(P)

       putenv - change or add a value to an environment

       #include <stdlib.h>

       int putenv(char *string);

       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 envi-
       ronment. 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 reen-
       trant is not required to be thread-safe.

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

       The putenv() function may fail if:

       ENOMEM Insufficient memory was available.

       The following sections are informative.

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

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

	      ret = putenv(var);

       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.

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


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

       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					PUTENV(P)

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