lib/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 #include <stdlib.h>
  31 #include <string.h>
  32 #if _LIBC || HAVE_UNISTD_H
  33 # include <unistd.h>
  34 #endif
  35
  36 #if !_LIBC
  37 # define __environ      environ
  38 # ifndef HAVE_ENVIRON_DECL
  39 extern char **environ;
  40 # endif
  41 #endif
  42
  43 #if _LIBC
  44 /* This lock protects against simultaneous modifications of `environ'.  */
  45 # include <bits/libc-lock.h>
  46 __libc_lock_define_initialized (static, envlock)
  47 # define LOCK   __libc_lock_lock (envlock)
  48 # define UNLOCK __libc_lock_unlock (envlock)
  49 #else
  50 # define LOCK
  51 # define UNLOCK
  52 #endif
  53
  54 /* In the GNU C library we must keep the namespace clean.  */
  55 #ifdef _LIBC
  56 # define unsetenv __unsetenv
  57 #endif
  58
  59
  60 int
  61 unsetenv (const char *name)
  62 {
  63   size_t len;
  64   char **ep;
  65
  66   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  67     {
  68       __set_errno (EINVAL);
  69       return -1;
  70     }
  71
  72   len = strlen (name);
  73
  74   LOCK;
  75
  76   ep = __environ;
  77   while (*ep != NULL)
  78     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  79       {
  80         /* Found it.  Remove this pointer by moving later ones back.  */
  81         char **dp = ep;
  82
  83         do
  84           dp[0] = dp[1];
  85         while (*dp++);
  86         /* Continue the loop in case NAME appears again.  */
  87       }
  88     else
  89       ++ep;
  90
  91   UNLOCK;
  92
  93   return 0;
  94 }
  95
  96 #ifdef _LIBC
  97 # undef unsetenv
  98 weak_alias (__unsetenv, unsetenv)
  99 #endif