gl/unsetenv.c

   1 /* Copyright (C) 1992,1995-1999,2000-2002 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include <errno.h>
  23 #if !_LIBC
  24 # if !defined errno && !defined HAVE_ERRNO_DECL
  25 extern int errno;
  26 # endif
  27 # define __set_errno(ev) ((errno) = (ev))
  28 #endif
  29
  30 #if _LIBC || HAVE_STDLIB_H
  31 # include <stdlib.h>
  32 #endif
  33 #if _LIBC || HAVE_STRING_H
  34 # include <string.h>
  35 #endif
  36 #if _LIBC || HAVE_UNISTD_H
  37 # include <unistd.h>
  38 #endif
  39
  40 #if !_LIBC
  41 # define __environ      environ
  42 # ifndef HAVE_ENVIRON_DECL
  43 extern char **environ;
  44 # endif
  45 #endif
  46
  47 #if _LIBC
  48 /* This lock protects against simultaneous modifications of `environ'.  */
  49 # include <bits/libc-lock.h>
  50 __libc_lock_define_initialized (static, envlock)
  51 # define LOCK   __libc_lock_lock (envlock)
  52 # define UNLOCK __libc_lock_unlock (envlock)
  53 #else
  54 # define LOCK
  55 # define UNLOCK
  56 #endif
  57
  58 /* In the GNU C library we must keep the namespace clean.  */
  59 #ifdef _LIBC
  60 # define unsetenv __unsetenv
  61 #endif
  62
  63
  64 int
  65 unsetenv (const char *name)
  66 {
  67   size_t len;
  68   char **ep;
  69
  70   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  71     {
  72       __set_errno (EINVAL);
  73       return -1;
  74     }
  75
  76   len = strlen (name);
  77
  78   LOCK;
  79
  80   ep = __environ;
  81   while (*ep != NULL)
  82     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  83       {
  84         /* Found it.  Remove this pointer by moving later ones back.  */
  85         char **dp = ep;
  86
  87         do
  88           dp[0] = dp[1];
  89         while (*dp++);
  90         /* Continue the loop in case NAME appears again.  */
  91       }
  92     else
  93       ++ep;
  94
  95   UNLOCK;
  96
  97   return 0;
  98 }
  99
 100 #ifdef _LIBC
 101 # undef unsetenv
 102 weak_alias (__unsetenv, unsetenv)
 103 #endif