stdio/gets.c

   1 /* Copyright (C) 1991, 1994, 1995, 1996 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
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <stdio.h>
  20 #include <errno.h>
  21 #include <string.h>
  22
  23 link_warning (gets,
  24               "the `gets' function is unreliable and should not be used.")
  25
  26 /* Read a newline-terminated string from stdin into S,
  27    removing the trailing newline.  Return S or NULL.  */
  28 char *
  29 gets (s)
  30      char *s;
  31 {
  32   register char *p = s;
  33   register int c;
  34   FILE *stream = stdin;
  35
  36   if (!__validfp (stream) || p == NULL)
  37     {
  38       __set_errno (EINVAL);
  39       return NULL;
  40     }
  41
  42   if (feof (stream) || ferror (stream))
  43     return NULL;
  44
  45   while ((c = getchar ()) != EOF)
  46     if (c == '\n')
  47       break;
  48     else
  49       *p++ = c;
  50
  51   *p = '\0';
  52
  53   /* Return null if we had an error, or if we got EOF
  54      before writing any characters.  */
  55
  56   if (ferror (stream) || (feof (stream) && p == s))
  57     return NULL;
  58
  59   return s;
  60 }