lib/unsetenv.c

   1 /* Copyright (C) 1992, 1995-2002, 2005-2013 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 of the License, or
   7    (at your option) 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
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
  20    optimizes away the name == NULL test below.  */
  21 #define _GL_ARG_NONNULL(params)
  22
  23 /* Specification.  */
  24 #include <stdlib.h>
  25
  26 #include <errno.h>
  27 #if !_LIBC
  28 # define __set_errno(ev) ((errno) = (ev))
  29 #endif
  30
  31 #include <string.h>
  32 #include <unistd.h>
  33
  34 #if !_LIBC
  35 # define __environ      environ
  36 #endif
  37
  38 #if _LIBC
  39 /* This lock protects against simultaneous modifications of 'environ'.  */
  40 # include <bits/libc-lock.h>
  41 __libc_lock_define_initialized (static, envlock)
  42 # define LOCK   __libc_lock_lock (envlock)
  43 # define UNLOCK __libc_lock_unlock (envlock)
  44 #else
  45 # define LOCK
  46 # define UNLOCK
  47 #endif
  48
  49 /* In the GNU C library we must keep the namespace clean.  */
  50 #ifdef _LIBC
  51 # define unsetenv __unsetenv
  52 #endif
  53
  54 #if _LIBC || !HAVE_UNSETENV
  55
  56 int
  57 unsetenv (const char *name)
  58 {
  59   size_t len;
  60   char **ep;
  61
  62   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  63     {
  64       __set_errno (EINVAL);
  65       return -1;
  66     }
  67
  68   len = strlen (name);
  69
  70   LOCK;
  71
  72   ep = __environ;
  73   while (*ep != NULL)
  74     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  75       {
  76         /* Found it.  Remove this pointer by moving later ones back.  */
  77         char **dp = ep;
  78
  79         do
  80           dp[0] = dp[1];
  81         while (*dp++);
  82         /* Continue the loop in case NAME appears again.  */
  83       }
  84     else
  85       ++ep;
  86
  87   UNLOCK;
  88
  89   return 0;
  90 }
  91
  92 #ifdef _LIBC
  93 # undef unsetenv
  94 weak_alias (__unsetenv, unsetenv)
  95 #endif
  96
  97 #else /* HAVE_UNSETENV */
  98
  99 # undef unsetenv
 100 # if !HAVE_DECL_UNSETENV
 101 #  if VOID_UNSETENV
 102 extern void unsetenv (const char *);
 103 #  else
 104 extern int unsetenv (const char *);
 105 #  endif
 106 # endif
 107
 108 /* Call the underlying unsetenv, in case there is hidden bookkeeping
 109    that needs updating beyond just modifying environ.  */
 110 int
 111 rpl_unsetenv (const char *name)
 112 {
 113   int result = 0;
 114   if (!name || !*name || strchr (name, '='))
 115     {
 116       errno = EINVAL;
 117       return -1;
 118     }
 119   while (getenv (name))
 120 # if !VOID_UNSETENV
 121     result =
 122 # endif
 123       unsetenv (name);
 124   return result;
 125 }
 126
 127 #endif /* HAVE_UNSETENV */