newlib/libc/stdlib/getenv_r.c

   1 /*
   2 FUNCTION
   3 <<_getenv_r>>---look up environment variable
   4
   5 INDEX
   6         _getenv_r
   7 INDEX
   8         environ
   9
  10 SYNOPSIS
  11         #include <stdlib.h>
  12         char *_getenv_r(struct _reent *<[reent_ptr]>, const char *<[name]>);
  13
  14 DESCRIPTION
  15 <<_getenv_r>> searches the list of environment variable names and values
  16 (using the global pointer ``<<char **environ>>'') for a variable whose
  17 name matches the string at <[name]>.  If a variable name matches,
  18 <<_getenv_r>> returns a pointer to the associated value.
  19
  20 RETURNS
  21 A pointer to the (string) value of the environment variable, or
  22 <<NULL>> if there is no such environment variable.
  23
  24 PORTABILITY
  25 <<_getenv_r>> is not ANSI; the rules for properly forming names of environment
  26 variables vary from one system to another.  This implementation does not
  27 permit '=' to be in identifiers.
  28
  29 <<_getenv_r>> requires a global pointer <<environ>>.
  30 */
  31
  32 /* This file may have been modified by DJ Delorie (Jan 1991).  If so,
  33 ** these modifications are Copyright (C) 1991 DJ Delorie.
  34 */
  35
  36 /*
  37  * Copyright (c) 1987 Regents of the University of California.
  38  * All rights reserved.
  39  *
  40  * Redistribution and use in source and binary forms are permitted
  41  * provided that: (1) source distributions retain this entire copyright
  42  * notice and comment, and (2) distributions including binaries display
  43  * the following acknowledgement:  ``This product includes software
  44  * developed by the University of California, Berkeley and its contributors''
  45  * in the documentation or other materials provided with the distribution.
  46  * Neither the name of the University nor the names of its
  47  * contributors may be used to endorse or promote products derived
  48  * from this software without specific prior written permission.
  49  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  50  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  51  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  52  */
  53
  54 #include <stdlib.h>
  55 #include <stddef.h>
  56 #include <string.h>
  57 #include "envlock.h"
  58
  59 extern char **environ;
  60
  61 /* Only deal with a pointer to environ, to work around subtle bugs with shared
  62    libraries and/or small data systems where the user declares his own
  63    'environ'.  */
  64 static char ***p_environ = &environ;
  65
  66 /*
  67  * _findenv --
  68  *      Returns pointer to value associated with name, if any, else NULL.
  69  *      Sets offset to be the offset of the name/value combination in the
  70  *      environmental array, for use by setenv(3) and unsetenv(3).
  71  *
  72  *      This routine *should* be a static; don't use it.
  73  */
  74
  75 char *
  76 _findenv_r (struct _reent *reent_ptr,
  77         register const char *name,
  78         int *offset)
  79 {
  80   register int len;
  81   register char **p;
  82   const char *c;
  83
  84   ENV_LOCK;
  85
  86   /* In some embedded systems, this does not get set.  This protects
  87      newlib from dereferencing a bad pointer.  */
  88   if (!*p_environ)
  89     {
  90       ENV_UNLOCK;
  91       return NULL;
  92     }
  93
  94   c = name;
  95   while (*c && *c != '=')  c++;
  96
  97   /* Identifiers may not contain an '=', so cannot match if does */
  98   if(*c != '=')
  99     {
 100     len = c - name;
 101     for (p = *p_environ; *p; ++p)
 102       if (!strncmp (*p, name, len))
 103         if (*(c = *p + len) == '=')
 104         {
 105           *offset = p - *p_environ;
 106           ENV_UNLOCK;
 107           return (char *) (++c);
 108         }
 109     }
 110   ENV_UNLOCK;
 111   return NULL;
 112 }
 113
 114 /*
 115  * _getenv_r --
 116  *      Returns ptr to value associated with name, if any, else NULL.
 117  */
 118
 119 char *
 120 _getenv_r (struct _reent *reent_ptr,
 121         const char *name)
 122 {
 123   int offset;
 124
 125   return _findenv_r (reent_ptr, name, &offset);
 126 }