mirror of https://github.com/mkerrisk/man-pages
121 lines
3.4 KiB
Groff
121 lines
3.4 KiB
Groff
.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" Modified Wed Jul 28 11:12:07 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Fri Sep 8 15:48:13 1995 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified 2013-12-31, David Malcolm <dmalcolm@redhat.com>
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.\" Split gets(3) into its own page; fgetc() et al. move to fgetc(3)
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.TH GETS 3 2017-09-15 "GNU" "Linux Programmer's Manual"
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.SH NAME
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gets \- get a string from standard input (DEPRECATED)
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.SH SYNOPSIS
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.nf
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.B #include <stdio.h>
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.PP
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.BI "char *gets(char *" "s" );
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.fi
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.SH DESCRIPTION
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.IR "Never use this function" .
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.PP
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.BR gets ()
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reads a line from
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.I stdin
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into the buffer pointed to by
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.I s
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until either a terminating newline or
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.BR EOF ,
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which it replaces with a null byte (\(aq\e0\(aq).
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No check for buffer overrun is performed (see BUGS below).
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.SH RETURN VALUE
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.BR gets ()
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returns
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.I s
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on success, and NULL
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on error or when end of file occurs while no characters have been read.
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However, given the lack of buffer overrun checking, there can be no
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guarantees that the function will even return.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR gets ()
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T} Thread safety MT-Safe
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.TE
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.sp 1
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.SH CONFORMING TO
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C89, C99, POSIX.1-2001.
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.PP
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LSB deprecates
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.BR gets ().
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POSIX.1-2008 marks
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.BR gets ()
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obsolescent.
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ISO C11 removes the specification of
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.BR gets ()
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from the C language, and since version 2.16,
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glibc header files don't expose the function declaration if the
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.B _ISOC11_SOURCE
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feature test macro is defined.
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.SH BUGS
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Never use
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.BR gets ().
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Because it is impossible to tell without knowing the data in advance how many
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characters
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.BR gets ()
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will read, and because
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.BR gets ()
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will continue to store characters past the end of the buffer,
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it is extremely dangerous to use.
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It has been used to break computer security.
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Use
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.BR fgets ()
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instead.
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.PP
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For more information, see CWE-242 (aka "Use of Inherently Dangerous
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Function") at
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http://cwe.mitre.org/data/definitions/242.html
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.SH SEE ALSO
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.BR read (2),
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.BR write (2),
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.BR ferror (3),
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.BR fgetc (3),
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.BR fgets (3),
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.BR fgetwc (3),
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.BR fgetws (3),
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.BR fopen (3),
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.BR fread (3),
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.BR fseek (3),
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.BR getline (3),
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.BR getwchar (3),
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.BR puts (3),
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.BR scanf (3),
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.BR ungetwc (3),
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.BR unlocked_stdio (3),
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.BR feature_test_macros (7)
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