lib/libc/stdlib/setenv.c

   1 /*
   2  * Copyright (c) 1987, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)setenv.c 8.1 (Berkeley) 6/4/93
  34  * $FreeBSD: src/lib/libc/stdlib/setenv.c,v 1.5.2.1 2000/09/20 19:46:03 brian Exp $
  35  * $DragonFly: src/lib/libc/stdlib/setenv.c,v 1.5 2005/04/28 13:51:55 joerg Exp $
  36  */
  37
  38 #include <stddef.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41
  42 extern char **environ;
  43
  44 char *__findenv (const char *, size_t *);
  45
  46 /*
  47  * setenv --
  48  *      Set the value of the environmental variable "name" to be
  49  *      "value".  If rewrite is set, replace any current value.
  50  */
  51 int
  52 setenv(const char *name, const char *value, int rewrite)
  53 {
  54         static char **alloced;                  /* if allocated space before */
  55         char *c;
  56         size_t l_value, offset;
  57
  58         if (*value == '=')                      /* no `=' in value */
  59                 ++value;
  60         l_value = strlen(value);
  61         if ((c = __findenv(name, &offset))) {   /* find if already exists */
  62                 if (!rewrite)
  63                         return (0);
  64                 if (strlen(c) >= l_value) {     /* old larger; copy over */
  65                         while ( (*c++ = *value++) );
  66                         return (0);
  67                 }
  68         } else {                                        /* create new slot */
  69                 int cnt;
  70                 char **p;
  71
  72                 for (p = environ, cnt = 0; *p; ++p, ++cnt);
  73                 if (alloced == environ) {
  74                         /* just increase size */
  75                         p = realloc(environ, sizeof(char *) * (cnt + 2));
  76                         if (p == NULL)
  77                                 return (-1);
  78                         alloced = environ = p;
  79                 }
  80                 else {                          /* get new space */
  81                                                 /* copy old entries into it */
  82                         p = malloc(sizeof(char *) * (cnt + 2));
  83                         if (p == NULL)
  84                                 return (-1);
  85                         bcopy(environ, p, cnt * sizeof(char *));
  86                         alloced = environ = p;
  87                 }
  88                 environ[cnt + 1] = NULL;
  89                 offset = cnt;
  90         }
  91         for (c = (char *)name; *c && *c != '='; ++c);   /* no `=' in name */
  92         if (!(environ[offset] =                 /* name + `=' + value */
  93             malloc((size_t)((int)(c - name) + l_value + 2))))
  94                 return (-1);
  95         for (c = environ[offset]; (*c = *name++) && *c != '='; ++c);
  96         for (*c++ = '='; (*c++ = *value++); );
  97         return (0);
  98 }
  99
 100 /*
 101  * unsetenv(name) --
 102  *      Delete environmental variable "name".
 103  */
 104 void
 105 unsetenv(const char *name)
 106 {
 107         char **p;
 108         size_t offset;
 109
 110         while (__findenv(name, &offset))        /* if set multiple times */
 111                 for (p = &environ[offset];; ++p)
 112                         if (!(*p = *(p + 1)))
 113                                 break;
 114 }