sysdeps/generic/setenv.c

   1 /* Copyright (C) 1992, 1995, 1996 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 #include <config.h>
  21 #endif
  22
  23 #include <errno.h>
  24
  25 #if _LIBC || HAVE_STDLIB_H
  26 #include <stdlib.h>
  27 #endif
  28 #if _LIBC || HAVE_STRING_H
  29 #include <string.h>
  30 #endif
  31 #if _LIBC || HAVE_UNISTD_H
  32 #include <unistd.h>
  33 #endif
  34
  35 #if _LIBC - 0 == 0
  36 #define __environ       environ
  37 #endif
  38
  39 #if _LIBC - 0
  40 /* This lock protects against simultaneous modifications of `environ'.  */
  41 #include <libc-lock.h>
  42 __libc_lock_define_initialized (static, envlock)
  43 #define LOCK    __libc_lock_lock (envlock)
  44 #define UNLOCK  __libc_lock_unlock (envlock)
  45 #else
  46 #define LOCK
  47 #define UNLOCK
  48 #endif
  49
  50 int
  51 setenv (name, value, replace)
  52      const char *name;
  53      const char *value;
  54      int replace;
  55 {
  56   register char **ep;
  57   register size_t size;
  58   const size_t namelen = strlen (name);
  59   const size_t vallen = strlen (value) + 1;
  60
  61   LOCK;
  62
  63   size = 0;
  64   for (ep = __environ; *ep != NULL; ++ep)
  65     if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
  66       break;
  67     else
  68       ++size;
  69
  70   if (*ep == NULL)
  71     {
  72       static char **last_environ;
  73       char **new_environ;
  74       if (__environ == last_environ)
  75         /* We allocated this space; we can extend it.  */
  76         new_environ = (char **) realloc (last_environ,
  77                                          (size + 2) * sizeof (char *));
  78       else
  79         new_environ = (char **) malloc ((size + 2) * sizeof (char *));
  80
  81       if (new_environ == NULL)
  82         {
  83           UNLOCK;
  84           return -1;
  85         }
  86
  87       new_environ[size] = malloc (namelen + 1 + vallen);
  88       if (new_environ[size] == NULL)
  89         {
  90           free ((char *) new_environ);
  91           errno = ENOMEM;
  92           UNLOCK;
  93           return -1;
  94         }
  95
  96       if (__environ != last_environ)
  97         memcpy ((char *) new_environ, (char *) __environ,
  98                 size * sizeof (char *));
  99
 100       memcpy (new_environ[size], name, namelen);
 101       new_environ[size][namelen] = '=';
 102       memcpy (&new_environ[size][namelen + 1], value, vallen);
 103
 104       new_environ[size + 1] = NULL;
 105
 106       last_environ = __environ = new_environ;
 107     }
 108   else if (replace)
 109     {
 110       size_t len = strlen (*ep);
 111       if (len + 1 < namelen + 1 + vallen)
 112         {
 113           /* The existing string is too short; malloc a new one.  */
 114           char *new = malloc (namelen + 1 + vallen);
 115           if (new == NULL)
 116             {
 117               UNLOCK;
 118               return -1;
 119             }
 120           *ep = new;
 121         }
 122       memcpy (*ep, name, namelen);
 123       (*ep)[namelen] = '=';
 124       memcpy (&(*ep)[namelen + 1], value, vallen);
 125     }
 126
 127   UNLOCK;
 128
 129   return 0;
 130 }
 131
 132 void
 133 unsetenv (name)
 134      const char *name;
 135 {
 136   const size_t len = strlen (name);
 137   char **ep;
 138
 139   LOCK;
 140
 141   for (ep = __environ; *ep; ++ep)
 142     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 143       {
 144         /* Found it.  Remove this pointer by moving later ones back.  */
 145         char **dp = ep;
 146         do
 147           dp[0] = dp[1];
 148         while (*dp++);
 149         /* Continue the loop in case NAME appears again.  */
 150       }
 151
 152   UNLOCK;
 153 }