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    Command:

    putenv

    
    
    

    SYNOPSIS

           #include <stdlib.h>
    
           int putenv(char *string);
    
       Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
    
           putenv(): _SVID_SOURCE || _XOPEN_SOURCE
    
    
    

    DESCRIPTION

           The  putenv()  function  adds or changes the value of environment vari-
           ables.  The argument string is of the form name=value.   If  name  does
           not already exist in the environment, then string is added to the envi-
           ronment.  If name does exist, then the value of name in the environment
           is  changed  to value.  The string pointed to by string becomes part of
           the environment, so altering the string changes the environment.
    
    
    

    RETURN VALUE

           The putenv() function returns zero on success, or nonzero if  an  error
           occurs.   In the event of an error, errno is set to indicate the cause.
    
    
    

    ERRORS

           ENOMEM Insufficient space to allocate new environment.
    
    
    

    CONFORMING TO

           SVr4, POSIX.1-2001, 4.3BSD.
    
    
    

    NOTES

           The putenv() function is not required to be reentrant, and the  one  in
           libc4, libc5 and glibc 2.0 is not, but the glibc 2.1 version is.
    
           Description  for  libc4, libc5, glibc: If the argument string is of the
           form name, and does not contain an '='  character,  then  the  variable
           name  is  removed  from the environment.  If putenv() has to allocate a
           new array environ,  and  the  previous  array  was  also  allocated  by
           putenv(), then it will be freed.  In no case will the old storage asso-
           ciated to the environment variable itself be freed.
    
           The libc4 and libc5 and glibc 2.1.2  versions  conform  to  SUSv2:  the
           pointer  string  given to putenv() is used.  In particular, this string
           becomes part of the environment; changing  it  later  will  change  the
           environment.   (Thus,  it is an error is to call putenv() with an auto-
           matic variable as the argument, then return from the  calling  function
           while  string  is  still  part  of  the  environment.)   However, glibc
           2.0-2.1.1 differs: a copy of the string is used.  On the one hand  this
           causes  a  memory  leak, and on the other hand it violates SUSv2.  This
           has been fixed in glibc 2.1.2.
    
           The 4.4BSD version, like glibc 2.0, uses a copy.
    
           SUSv2 removes the const from the prototype, and so does glibc 2.1.3.
    
    
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