Standard C Library Functions                           putenv(3C)



NAME
     putenv - change or add value to environment

SYNOPSIS
     #include 

     int putenv(char *string);


DESCRIPTION
     The putenv() function makes the  value  of  the  environment
     variable  name  equal to value by altering an existing vari-
     able 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.

ERORS
     The putenv() function may fail if:

     ENOMEM    Insufficient memory was available.


USAGE
     The  putenv()  function  can  be  safely  called  from  mul-
     tithreaded  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 environment list
     using putenv() or getenv().





SunOS 5.11           Last change: 7 Aug 2004                    1






Standard C Library Functions                           putenv(3C)



ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Standard                    
    
     MT-Level                     Safe                        
    


SEE ALSO
     exec(2), getenv(3C), malloc(3C), attributes(5),  environ(5),
     standards(5)

WARNINGS
     The string argument should not be an automatic variable.  It
     should  be  declared static if it is declared within a func-
     tion because it cannot be automatically declared.  A  poten-
     tial  error  is  to  call  putenv()  with  a  pointer  to an
     automatic variable as the argument and to then exit the cal-
     ling function while string is still part of the environment.





























SunOS 5.11           Last change: 7 Aug 2004                    2