getenv.c

来自「一个C源代码分析器」· C语言 代码 · 共 45 行

/* Copyright (C) 1991, 1992, 1994 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <ansidecl.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifndef	HAVE_GNU_LD
#define	__environ	environ
#endif

/* Return the value of the environment variable NAME.  */
char *
DEFUN(getenv, (name), register CONST char *name)
{
  register CONST size_t len = strlen(name);
  register char **ep;

  if (__environ == NULL)
    return NULL;

  for (ep = __environ; *ep != NULL; ++ep)
    if (!strncmp(*ep, name, len) && (*ep)[len] == '=')
      return &(*ep)[len + 1];

  return NULL;
}