lib/setenv.c

   1 /* Copyright (C) 1992, 1995, 2000 Free Software Foundation, Inc.
   2
   3 NOTE: The canonical source of this file is maintained with the GNU C Library.
   4 Bugs can be reported to bug-glibc@prep.ai.mit.edu.
   5
   6 This program is free software; you can redistribute it and/or modify it
   7 under the terms of the GNU General Public License as published by the
   8 Free Software Foundation; either version 2, or (at your option) any
   9 later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  19 USA.  */
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <errno.h>
  26
  27 #if _LIBC || HAVE_STDLIB_H
  28 # include <stdlib.h>
  29 #endif
  30 #if _LIBC || HAVE_STRING_H
  31 # include <string.h>
  32 #endif
  33 #if _LIBC || HAVE_UNISTD_H
  34 # include <unistd.h>
  35 #endif
  36
  37 #ifndef HAVE_GNU_LD
  38 # define __environ      environ
  39 #endif
  40
  41 int
  42 setenv (name, value, replace)
  43      const char *name;
  44      const char *value;
  45      int replace;
  46 {
  47   register char **ep;
  48   register size_t size;
  49   const size_t namelen = strlen (name);
  50   const size_t vallen = strlen (value) + 1;
  51
  52   size = 0;
  53   for (ep = __environ; *ep != NULL; ++ep)
  54     if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
  55       break;
  56     else
  57       ++size;
  58
  59   if (*ep == NULL)
  60     {
  61       static char **last_environ;
  62       char **new_environ;
  63       if (__environ == last_environ)
  64         /* We allocated this space; we can extend it.  */
  65         new_environ = (char **) realloc (last_environ,
  66                                          (size + 2) * sizeof (char *));
  67       else
  68         new_environ = (char **) malloc ((size + 2) * sizeof (char *));
  69
  70       if (new_environ == NULL)
  71         return -1;
  72
  73       new_environ[size] = malloc (namelen + 1 + vallen);
  74       if (new_environ[size] == NULL)
  75         {
  76           free ((char *) new_environ);
  77           errno = ENOMEM;
  78           return -1;
  79         }
  80
  81       if (__environ != last_environ)
  82         memcpy ((char *) new_environ, (char *) __environ,
  83                 size * sizeof (char *));
  84
  85       memcpy (new_environ[size], name, namelen);
  86       new_environ[size][namelen] = '=';
  87       memcpy (&new_environ[size][namelen + 1], value, vallen);
  88
  89       new_environ[size + 1] = NULL;
  90
  91       last_environ = __environ = new_environ;
  92     }
  93   else if (replace)
  94     {
  95       size_t len = strlen (*ep);
  96       if (len + 1 < namelen + 1 + vallen)
  97         {
  98           /* The existing string is too short; malloc a new one.  */
  99           char *new = malloc (namelen + 1 + vallen);
 100           if (new == NULL)
 101             return -1;
 102           *ep = new;
 103         }
 104       memcpy (*ep, name, namelen);
 105       (*ep)[namelen] = '=';
 106       memcpy (&(*ep)[namelen + 1], value, vallen);
 107     }
 108
 109   return 0;
 110 }
 111
 112 void
 113 unsetenv (name)
 114      const char *name;
 115 {
 116   const size_t len = strlen (name);
 117   char **ep;
 118
 119   for (ep = __environ; *ep; ++ep)
 120     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 121       {
 122         /* Found it.  Remove this pointer by moving later ones back.  */
 123         char **dp = ep;
 124         do
 125           dp[0] = dp[1];
 126         while (*dp++);
 127         /* Continue the loop in case NAME appears again.  */
 128       }
 129 }