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    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 #if !_LIBC
  25 # if !defined errno && !defined HAVE_ERRNO_DECL
  26 extern int errno;
  27 # endif
  28 # define __set_errno(ev) ((errno) = (ev))
  29 #endif
  30
  31 #if _LIBC || HAVE_STDLIB_H
  32 # include <stdlib.h>
  33 #endif
  34 #if _LIBC || HAVE_STRING_H
  35 # include <string.h>
  36 #endif
  37 #if _LIBC || HAVE_UNISTD_H
  38 # include <unistd.h>
  39 #endif
  40
  41 #if !_LIBC
  42 # define __environ      environ
  43 # ifndef HAVE_ENVIRON_DECL
  44 extern char **environ;
  45 # endif
  46 #endif
  47
  48 #if _LIBC
  49 /* This lock protects against simultaneous modifications of `environ'.  */
  50 # include <bits/libc-lock.h>
  51 __libc_lock_define_initialized (static, envlock)
  52 # define LOCK   __libc_lock_lock (envlock)
  53 # define UNLOCK __libc_lock_unlock (envlock)
  54 #else
  55 # define LOCK
  56 # define UNLOCK
  57 #endif
  58
  59 /* In the GNU C library we must keep the namespace clean.  */
  60 #ifdef _LIBC
  61 # define unsetenv __unsetenv
  62 #endif
  63
  64
  65 int
  66 unsetenv (const char *name)
  67 {
  68   size_t len;
  69   char **ep;
  70
  71   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  72     {
  73       __set_errno (EINVAL);
  74       return -1;
  75     }
  76
  77   len = strlen (name);
  78
  79   LOCK;
  80
  81   ep = __environ;
  82   while (*ep != NULL)
  83     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  84       {
  85         /* Found it.  Remove this pointer by moving later ones back.  */
  86         char **dp = ep;
  87
  88         do
  89           dp[0] = dp[1];
  90         while (*dp++);
  91         /* Continue the loop in case NAME appears again.  */
  92       }
  93     else
  94       ++ep;
  95
  96   UNLOCK;
  97
  98   return 0;
  99 }
 100
 101 #ifdef _LIBC
 102 # undef unsetenv
 103 weak_alias (__unsetenv, unsetenv)
 104 #endif