putenv(3p) - phpMan

PUTENV(P)                                                            PUTENV(P)



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 appli-
       cations.

       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 environ-
       ment.

       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 .



POSIX                                2003                            PUTENV(P)

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