man3/gets.3

   1 .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" Modified Wed Jul 28 11:12:07 1993 by Rik Faith (faith@cs.unc.edu)
   6 .\" Modified Fri Sep  8 15:48:13 1995 by Andries Brouwer (aeb@cwi.nl)
   7 .\" Modified 2013-12-31, David Malcolm <dmalcolm@redhat.com>
   8 .\"     Split gets(3) into its own page; fgetc() et al. move to fgetc(3)
   9 .TH GETS 3  2021-03-22 "Linux man-pages (unreleased)" "Linux Programmer's Manual"
  10 .SH NAME
  11 gets \- get a string from standard input (DEPRECATED)
  12 .SH LIBRARY
  13 Standard C library
  14 .RI ( libc ", " \-lc )
  15 .SH SYNOPSIS
  16 .nf
  17 .B #include <stdio.h>
  18 .PP
  19 .BI "char *gets(char *" "s" );
  20 .fi
  21 .SH DESCRIPTION
  22 .IR "Never use this function" .
  23 .PP
  24 .BR gets ()
  25 reads a line from
  26 .I stdin
  27 into the buffer pointed to by
  28 .I s
  29 until either a terminating newline or
  30 .BR EOF ,
  31 which it replaces with a null byte (\(aq\e0\(aq).
  32 No check for buffer overrun is performed (see BUGS below).
  33 .SH RETURN VALUE
  34 .BR gets ()
  35 returns
  36 .I s
  37 on success, and NULL
  38 on error or when end of file occurs while no characters have been read.
  39 However, given the lack of buffer overrun checking, there can be no
  40 guarantees that the function will even return.
  41 .SH ATTRIBUTES
  42 For an explanation of the terms used in this section, see
  43 .BR attributes (7).
  44 .ad l
  45 .nh
  46 .TS
  47 allbox;
  48 lbx lb lb
  49 l l l.
  50 Interface       Attribute       Value
  51 T{
  52 .BR gets ()
  53 T}      Thread safety   MT-Safe
  54 .TE
  55 .hy
  56 .ad
  57 .sp 1
  58 .SH STANDARDS
  59 C89, C99, POSIX.1-2001.
  60 .PP
  61 LSB deprecates
  62 .BR gets ().
  63 POSIX.1-2008 marks
  64 .BR gets ()
  65 obsolescent.
  66 ISO C11 removes the specification of
  67 .BR gets ()
  68 from the C language, and since version 2.16,
  69 glibc header files don't expose the function declaration if the
  70 .B _ISOC11_SOURCE
  71 feature test macro is defined.
  72 .SH BUGS
  73 Never use
  74 .BR gets ().
  75 Because it is impossible to tell without knowing the data in advance how many
  76 characters
  77 .BR gets ()
  78 will read, and because
  79 .BR gets ()
  80 will continue to store characters past the end of the buffer,
  81 it is extremely dangerous to use.
  82 It has been used to break computer security.
  83 Use
  84 .BR fgets ()
  85 instead.
  86 .PP
  87 For more information, see CWE-242 (aka "Use of Inherently Dangerous
  88 Function") at
  89 http://cwe.mitre.org/data/definitions/242.html
  90 .SH SEE ALSO
  91 .BR read (2),
  92 .BR write (2),
  93 .BR ferror (3),
  94 .BR fgetc (3),
  95 .BR fgets (3),
  96 .BR fgetwc (3),
  97 .BR fgetws (3),
  98 .BR fopen (3),
  99 .BR fread (3),
 100 .BR fseek (3),
 101 .BR getline (3),
 102 .BR getwchar (3),
 103 .BR puts (3),
 104 .BR scanf (3),
 105 .BR ungetwc (3),
 106 .BR unlocked_stdio (3),
 107 .BR feature_test_macros (7)