gl/unsetenv.c

   1 /* Copyright (C) 1992,1995-1999,2000-2002,2005-2006 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 3, 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, see <http://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 #include <errno.h>
  20 #if !_LIBC
  21 # define __set_errno(ev) ((errno) = (ev))
  22 #endif
  23
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27
  28 #if !_LIBC
  29 # define __environ      environ
  30 # ifndef HAVE_ENVIRON_DECL
  31 extern char **environ;
  32 # endif
  33 #endif
  34
  35 #if _LIBC
  36 /* This lock protects against simultaneous modifications of `environ'.  */
  37 # include <bits/libc-lock.h>
  38 __libc_lock_define_initialized (static, envlock)
  39 # define LOCK   __libc_lock_lock (envlock)
  40 # define UNLOCK __libc_lock_unlock (envlock)
  41 #else
  42 # define LOCK
  43 # define UNLOCK
  44 #endif
  45
  46 /* In the GNU C library we must keep the namespace clean.  */
  47 #ifdef _LIBC
  48 # define unsetenv __unsetenv
  49 #endif
  50
  51
  52 int
  53 unsetenv (const char *name)
  54 {
  55   size_t len;
  56   char **ep;
  57
  58   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  59     {
  60       __set_errno (EINVAL);
  61       return -1;
  62     }
  63
  64   len = strlen (name);
  65
  66   LOCK;
  67
  68   ep = __environ;
  69   while (*ep != NULL)
  70     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  71       {
  72         /* Found it.  Remove this pointer by moving later ones back.  */
  73         char **dp = ep;
  74
  75         do
  76           dp[0] = dp[1];
  77         while (*dp++);
  78         /* Continue the loop in case NAME appears again.  */
  79       }
  80     else
  81       ++ep;
  82
  83   UNLOCK;
  84
  85   return 0;
  86 }
  87
  88 #ifdef _LIBC
  89 # undef unsetenv
  90 weak_alias (__unsetenv, unsetenv)
  91 #endif