dmake/unix/sysvr1/putenv.c

   1 /* RCS  $Id: putenv.c,v 1.1.1.1 2000-09-22 15:33:35 hr Exp $
   2 --
   3 -- SYNOPSIS
   4 --      My own putenv for BSD like systems.
   5 --
   6 -- DESCRIPTION
   7 --  This originally came from MKS, but I rewrote it to fix a bug with
   8 --  replacing existing strings, probably never happened but the code
   9 --  was wrong nonetheless.
  10 --
  11 -- AUTHOR
  12 --      Dennis Vadura, dvadura@dmake.wticorp.com
  13 --
  14 -- WWW
  15 --      http://dmake.wticorp.com/
  16 --
  17 -- COPYRIGHT
  18 --      Copyright (c) 1996,1997 by WTI Corp.  All rights reserved.
  19 --
  20 --      This program is NOT free software; you can redistribute it and/or
  21 --      modify it under the terms of the Software License Agreement Provided
  22 --      in the file <distribution-root>/readme/license.txt.
  23 --
  24 -- LOG
  25 --      Use cvs log to obtain detailed change logs.
  26 */
  27
  28 #include <stdio.h>
  29 #include <string.h>
  30
  31 int
  32 putenv( str )/*
  33 ===============
  34    Take a string of the form NAME=value and stick it into the environment.
  35    We do this by allocating a new set of pointers if we have to add a new
  36    string and by replacing an existing pointer if the value replaces the value
  37    of an existing string. */
  38 char *str;
  39 {
  40    extern char **environ;       /* The current environment. */
  41    static char **ourenv = NULL;     /* A new environment        */
  42    register char **p;
  43    register char *q;
  44    int      size;
  45
  46    /* First search the current environment and see if we can replace a
  47     * string. */
  48    for( p=environ; *p; p++ ) {
  49       register char *s = str;
  50
  51       for( q = *p; *q && *s && *s == *q; q++, s++ )
  52      if( *s == '=' ) {
  53         *p = str;
  54         return(0);          /* replaced it so go away */
  55      }
  56    }
  57
  58    /* Ok, can't replace a string so need to grow the environment. */
  59    size = p - environ + 2;  /* size of new environment */
  60                 /* size of old is size-1   */
  61
  62    /* It's the first time, so allocate a new environment since we don't know
  63     * where the old one is comming from. */
  64    if( ourenv == NULL ) {
  65       if( (ourenv = (char **) malloc( sizeof(char *)*size )) == NULL )
  66      return(1);
  67
  68       memcpy( (char *)ourenv, (char *)environ, (size-2)*sizeof(char *) );
  69    }
  70    else if( (ourenv = (char **)realloc( ourenv, size*sizeof(char *))) == NULL )
  71       return(1);
  72
  73    ourenv[--size] = NULL;
  74    ourenv[--size] = str;
  75
  76    environ = ourenv;
  77    return(0);
  78 }