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 not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #if 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 /* If this variable is not a null pointer we allocated the current
  51    environment.  */
  52 static char **last_environ;
  53
  54
  55 int
  56 setenv (name, value, replace)
  57      const char *name;
  58      const char *value;
  59      int replace;
  60 {
  61   register char **ep;
  62   register size_t size;
  63   const size_t namelen = strlen (name);
  64   const size_t vallen = strlen (value) + 1;
  65
  66   LOCK;
  67
  68   size = 0;
  69   if (__environ != NULL)
  70     for (ep = __environ; *ep != NULL; ++ep)
  71       if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
  72         break;
  73       else
  74         ++size;
  75
  76   if (__environ == NULL || *ep == NULL)
  77     {
  78       char **new_environ;
  79       if (__environ == last_environ && __environ != NULL)
  80         /* We allocated this space; we can extend it.  */
  81         new_environ = (char **) realloc (last_environ,
  82                                          (size + 2) * sizeof (char *));
  83       else
  84         new_environ = (char **) malloc ((size + 2) * sizeof (char *));
  85
  86       if (new_environ == NULL)
  87         {
  88           UNLOCK;
  89           return -1;
  90         }
  91
  92       new_environ[size] = malloc (namelen + 1 + vallen);
  93       if (new_environ[size] == NULL)
  94         {
  95           free ((char *) new_environ);
  96           __set_errno (ENOMEM);
  97           UNLOCK;
  98           return -1;
  99         }
 100
 101       if (__environ != last_environ)
 102         memcpy ((char *) new_environ, (char *) __environ,
 103                 size * sizeof (char *));
 104
 105       memcpy (new_environ[size], name, namelen);
 106       new_environ[size][namelen] = '=';
 107       memcpy (&new_environ[size][namelen + 1], value, vallen);
 108
 109       new_environ[size + 1] = NULL;
 110
 111       last_environ = __environ = new_environ;
 112     }
 113   else if (replace)
 114     {
 115       size_t len = strlen (*ep);
 116       if (len + 1 < namelen + 1 + vallen)
 117         {
 118           /* The existing string is too short; malloc a new one.  */
 119           char *new = malloc (namelen + 1 + vallen);
 120           if (new == NULL)
 121             {
 122               UNLOCK;
 123               return -1;
 124             }
 125           *ep = new;
 126         }
 127       memcpy (*ep, name, namelen);
 128       (*ep)[namelen] = '=';
 129       memcpy (&(*ep)[namelen + 1], value, vallen);
 130     }
 131
 132   UNLOCK;
 133
 134   return 0;
 135 }
 136
 137 void
 138 unsetenv (name)
 139      const char *name;
 140 {
 141   const size_t len = strlen (name);
 142   char **ep;
 143
 144   LOCK;
 145
 146   for (ep = __environ; *ep; ++ep)
 147     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
 148       {
 149         /* Found it.  Remove this pointer by moving later ones back.  */
 150         char **dp = ep;
 151         do
 152           dp[0] = dp[1];
 153         while (*dp++);
 154         /* Continue the loop in case NAME appears again.  */
 155       }
 156
 157   UNLOCK;
 158 }
 159
 160 /* The `clearenv' was planned to be added to POSIX.1 but probably
 161    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
 162    for Fortran 77) requires this function.  */
 163 int
 164 clearenv ()
 165 {
 166   LOCK;
 167
 168   if (__environ == last_environ && __environ != NULL)
 169     {
 170       /* We allocated this environment so we can free it.  */
 171       free (__environ);
 172       last_environ = NULL;
 173     }
 174
 175   /* Clear the environment pointer removes the whole environment.  */
 176   __environ = NULL;
 177
 178   UNLOCK;
 179
 180   return 0;
 181 }