newlib/libc/stdio/gets.c

   1 /*
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms are permitted
   6  * provided that the above copyright notice and this paragraph are
   7  * duplicated in all such forms and that any documentation,
   8  * advertising materials, and other materials related to such
   9  * distribution and use acknowledge that the software was developed
  10  * by the University of California, Berkeley.  The name of the
  11  * University may not be used to endorse or promote products derived
  12  * from this software without specific prior written permission.
  13  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  16  */
  17
  18 /*
  19 FUNCTION
  20 <<gets>>---get character string (obsolete, use <<fgets>> instead)
  21
  22 INDEX
  23         gets
  24 INDEX
  25         _gets_r
  26
  27 ANSI_SYNOPSIS
  28         #include <stdio.h>
  29
  30         char *gets(char *<[buf]>);
  31
  32         char *_gets_r(struct _reent *<[reent]>, char *<[buf]>);
  33
  34 TRAD_SYNOPSIS
  35         #include <stdio.h>
  36
  37         char *gets(<[buf]>)
  38         char *<[buf]>;
  39
  40         char *_gets_r(<[reent]>, <[buf]>)
  41         struct _reent *<[reent]>;
  42         char *<[buf]>;
  43
  44 DESCRIPTION
  45         Reads characters from standard input until a newline is found.
  46         The characters up to the newline are stored in <[buf]>. The
  47         newline is discarded, and the buffer is terminated with a 0.
  48
  49         This is a @emph{dangerous} function, as it has no way of checking
  50         the amount of space available in <[buf]>. One of the attacks
  51         used by the Internet Worm of 1988 used this to overrun a
  52         buffer allocated on the stack of the finger daemon and
  53         overwrite the return address, causing the daemon to execute
  54         code downloaded into it over the connection.
  55
  56         The alternate function <<_gets_r>> is a reentrant version.  The extra
  57         argument <[reent]> is a pointer to a reentrancy structure.
  58
  59
  60 RETURNS
  61         <<gets>> returns the buffer passed to it, with the data filled
  62         in. If end of file occurs with some data already accumulated,
  63         the data is returned with no other indication. If end of file
  64         occurs with no data in the buffer, NULL is returned.
  65
  66 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
  67 <<lseek>>, <<read>>, <<sbrk>>, <<write>>.
  68 */
  69
  70 #include <_ansi.h>
  71 #include <reent.h>
  72 #include <stdio.h>
  73
  74 char *
  75 _DEFUN(_gets_r, (ptr, buf),
  76        struct _reent *ptr _AND
  77        char *buf)
  78 {
  79   register int c;
  80   register char *s = buf;
  81
  82   while ((c = _getchar_r (ptr)) != '\n')
  83     if (c == EOF)
  84       if (s == buf)
  85         return NULL;
  86       else
  87         break;
  88     else
  89       *s++ = c;
  90   *s = 0;
  91   return buf;
  92 }
  93
  94 #ifndef _REENT_ONLY
  95
  96 char *
  97 _DEFUN(gets, (buf),
  98        char *buf)
  99 {
 100   return _gets_r (_REENT, buf);
 101 }
 102
 103 #endif