lib/unsetenv.c

   1 /* Copyright (C) 1992, 1995-2002, 2005-2017 Free Software Foundation,
   2    Inc.
   3    This file is part of the GNU C Library.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
  19    optimizes away the name == NULL test below.  */
  20 #define _GL_ARG_NONNULL(params)
  21
  22 #include <config.h>
  23
  24 /* Specification.  */
  25 #include <stdlib.h>
  26
  27 #include <errno.h>
  28 #if !_LIBC
  29 # define __set_errno(ev) ((errno) = (ev))
  30 #endif
  31
  32 #include <string.h>
  33 #include <unistd.h>
  34
  35 #if !_LIBC
  36 # define __environ      environ
  37 #endif
  38
  39 #if _LIBC
  40 /* This lock protects against simultaneous modifications of 'environ'.  */
  41 # include <bits/libc-lock.h>
  42 __libc_lock_define_initialized (static, envlock)
  43 # define LOCK   __libc_lock_lock (envlock)
  44 # define UNLOCK __libc_lock_unlock (envlock)
  45 #else
  46 # define LOCK
  47 # define UNLOCK
  48 #endif
  49
  50 /* In the GNU C library we must keep the namespace clean.  */
  51 #ifdef _LIBC
  52 # define unsetenv __unsetenv
  53 #endif
  54
  55 #if _LIBC || !HAVE_UNSETENV
  56
  57 int
  58 unsetenv (const char *name)
  59 {
  60   size_t len;
  61   char **ep;
  62
  63   if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
  64     {
  65       __set_errno (EINVAL);
  66       return -1;
  67     }
  68
  69   len = strlen (name);
  70
  71   LOCK;
  72
  73   ep = __environ;
  74   while (*ep != NULL)
  75     if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
  76       {
  77         /* Found it.  Remove this pointer by moving later ones back.  */
  78         char **dp = ep;
  79
  80         do
  81           dp[0] = dp[1];
  82         while (*dp++);
  83         /* Continue the loop in case NAME appears again.  */
  84       }
  85     else
  86       ++ep;
  87
  88   UNLOCK;
  89
  90   return 0;
  91 }
  92
  93 #ifdef _LIBC
  94 # undef unsetenv
  95 weak_alias (__unsetenv, unsetenv)
  96 #endif
  97
  98 #else /* HAVE_UNSETENV */
  99
 100 # undef unsetenv
 101 # if !HAVE_DECL_UNSETENV
 102 #  if VOID_UNSETENV
 103 extern void unsetenv (const char *);
 104 #  else
 105 extern int unsetenv (const char *);
 106 #  endif
 107 # endif
 108
 109 /* Call the underlying unsetenv, in case there is hidden bookkeeping
 110    that needs updating beyond just modifying environ.  */
 111 int
 112 rpl_unsetenv (const char *name)
 113 {
 114   int result = 0;
 115   if (!name || !*name || strchr (name, '='))
 116     {
 117       errno = EINVAL;
 118       return -1;
 119     }
 120   while (getenv (name))
 121 # if !VOID_UNSETENV
 122     result =
 123 # endif
 124       unsetenv (name);
 125   return result;
 126 }
 127
 128 #endif /* HAVE_UNSETENV */