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root/usr/lib/libc/stdlib/setenv.c

DEFINITIONS

1. setenv
2. unsetenv

   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. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  30 #include <stddef.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  34 extern char **environ;
  36 char *__findenv(const char *, int *);
  38 /*
  39  * setenv --
  40  *      Set the value of the environmental variable "name" to be
  41  *      "value".  If rewrite is set, replace any current value.
  42  */
  43 int
setenv(name, value, rewrite)
  45         const char *name;
  46         const char *value;
  47         int rewrite;
  48 {
  49         static int alloced;                     /* if allocated space before */
  50         char *c;
  51         int l_value, offset;
  53         if (*value == '=')                      /* no `=' in value */
  54                 ++value;
l_value = strlen(value);
  56         if ((c = __findenv(name, &offset))) {   /* find if already exists */
  57                 if (!rewrite)
  58                         return (0);
  59                 if ((int)strlen(c) >= l_value) {        /* old larger; copy over */
  60                         while ( (*c++ = *value++) );
  61                         return (0);
  62                 }
  63         } else {                                        /* create new slot */
  64                 int cnt;
  65                 char **p;
  67                 for (p = environ, cnt = 0; *p; ++p, ++cnt);
  68                 if (alloced) {                  /* just increase size */
environ = (char **)realloc((char *)environ,
  70                             (size_t)(sizeof(char *) * (cnt + 2)));
  71                         if (!environ)
  72                                 return (-1);
  73                 }
  74                 else {                          /* get new space */
alloced = 1;            /* copy old entries into it */
p = malloc((size_t)(sizeof(char *) * (cnt + 2)));
  77                         if (!p)
  78                                 return (-1);
bcopy(environ, p, cnt * sizeof(char *));
environ = p;
  81                 }
environ[cnt + 1] = NULL;
offset = cnt;
  84         }
  85         for (c = (char *)name; *c && *c != '='; ++c);   /* no `=' in name */
  86         if (!(environ[offset] =                 /* name + `=' + value */
malloc((size_t)((int)(c - name) + l_value + 2))))
  88                 return (-1);
  89         for (c = environ[offset]; (*c = *name++) && *c != '='; ++c);
  90         for (*c++ = '='; (*c++ = *value++) != 0;);
  91         return (0);
  92 }
  94 /*
  95  * unsetenv(name) --
  96  *      Delete environmental variable "name".
  97  */
  98 void
  99 unsetenv(name)
 100         const char *name;
 101 {
 102         char **p;
 103         int offset;
 105         while (__findenv(name, &offset))        /* if set multiple times */
 106                 for (p = &environ[offset];; ++p)
 107                         if (!(*p = *(p + 1)))
 108                                 break;
 109 }