usr/src/lib/libbc/libc/gen/common/putenv.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1987 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*      LINTLIBRARY     */
  33 /*      putenv - change environment variables
  34  *
  35  *      input - char *change = a pointer to a string of the form
  36  *                             "name=value"
  37  *
  38  *      output - 0, if successful
  39  *               1, otherwise
  40  */
  41
  42 #include <stdio.h>
  43 #include <stdlib.h>
  44
  45 extern char **environ;          /* pointer to enviroment */
  46 static int      reall;          /* flag to reallocate space, if putenv is called
  47                                    more than once */
  48 static int      find(char *);
  49 static int      match(char *, char *);
  50
  51 int
  52 putenv(char *change)
  53 {
  54         char **newenv;              /* points to new environment */
  55         int which;          /* index of variable to replace */
  56
  57         if ((which = find(change)) < 0)  {
  58                 /* if a new variable */
  59                 /* which is negative of table size, so invert and
  60                    count new element */
  61                 which = (-which) + 1;
  62                 if (reall)  {
  63                         /* we have expanded environ before */
  64                         newenv = (char **)realloc(environ,
  65                                   which*sizeof(char *));
  66                         if (newenv == NULL)  return (-1);
  67                         /* now that we have space, change environ */
  68                         environ = newenv;
  69                 } else {
  70                         /* environ points to the original space */
  71                         reall++;
  72                         newenv = (char **)malloc(which*sizeof(char *));
  73                         if (newenv == NULL)  return (-1);
  74                         (void)memcpy((char *)newenv, (char *)environ,
  75                                 (int)(which*sizeof(char *)));
  76                         environ = newenv;
  77                 }
  78                 environ[which-2] = change;
  79                 environ[which-1] = NULL;
  80         }  else  {
  81                 /* we are replacing an old variable */
  82                 environ[which] = change;
  83         }
  84         return (0);
  85 }
  86
  87 /*      find - find where s2 is in environ
  88  *
  89  *      input - str = string of form name=value
  90  *
  91  *      output - index of name in environ that matches "name"
  92  *               -size of table, if none exists
  93 */
  94 static int
  95 find(char *str)
  96 {
  97         int ct = 0;     /* index into environ */
  98
  99         while(environ[ct] != NULL)   {
 100                 if (match(environ[ct], str)  != 0)
 101                         return (ct);
 102                 ct++;
 103         }
 104         return (-(++ct));
 105 }
 106 /*
 107  *      s1 is either name, or name=value
 108  *      s2 is name=value
 109  *      if names match, return value of 1,
 110  *      else return 0
 111  */
 112
 113 static int
 114 match(char *s1, char *s2)
 115 {
 116         while(*s1 == *s2++)  {
 117                 if (*s1 == '=')
 118                         return (1);
 119                 s1++;
 120         }
 121         return (0);
 122 }