fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
157 lines
4.1 KiB
Groff
157 lines
4.1 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)fgets.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd May 5, 2012
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.Dt FGETS 3
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.Os
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.Sh NAME
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.Nm fgets ,
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.Nm gets
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.Nd get a line from a stream
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdio.h
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.Ft char *
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.Fn fgets "char * restrict str" "int size" "FILE * restrict stream"
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.Ft char *
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.Fn gets "char *str"
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.Sh DESCRIPTION
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The
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.Fn fgets
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function
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reads at most one less than the number of characters specified by
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.Fa size
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from the given
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.Fa stream
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and stores them in the string
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.Fa str .
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Reading stops when a newline character is found,
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at end-of-file or error.
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The newline, if any, is retained.
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If any characters are read and there is no error, a
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.Ql \e0
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character is appended to end the string.
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.Pp
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The
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.Fn gets
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function
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is equivalent to
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.Fn fgets
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with an infinite
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.Fa size
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and a
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.Fa stream
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of
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.Dv stdin ,
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except that the newline character (if any) is not stored in the string.
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It is the caller's responsibility to ensure that the input line,
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if any, is sufficiently short to fit in the string.
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.Sh RETURN VALUES
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Upon successful completion,
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.Fn fgets
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and
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.Fn gets
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return
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a pointer to the string.
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If end-of-file occurs before any characters are read,
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they return
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.Dv NULL
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and the buffer contents remain unchanged.
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If an error occurs,
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they return
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.Dv NULL
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and the buffer contents are indeterminate.
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The
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.Fn fgets
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and
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.Fn gets
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functions
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do not distinguish between end-of-file and error, and callers must use
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.Xr feof 3
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and
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.Xr ferror 3
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to determine which occurred.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EBADF
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The given
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.Fa stream
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is not a readable stream.
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.El
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.Pp
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The function
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.Fn fgets
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may also fail and set
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.Va errno
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for any of the errors specified for the routines
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.Xr fflush 3 ,
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.Xr fstat 2 ,
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.Xr read 2 ,
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or
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.Xr malloc 3 .
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.Pp
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The function
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.Fn gets
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may also fail and set
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.Va errno
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for any of the errors specified for the routine
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.Xr getchar 3 .
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.Sh SEE ALSO
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.Xr feof 3 ,
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.Xr ferror 3 ,
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.Xr fgetln 3 ,
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.Xr fgetws 3 ,
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.Xr getline 3
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.Sh STANDARDS
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The functions
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.Fn fgets
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and
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.Fn gets
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conform to
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.St -isoC-99 .
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.Sh SECURITY CONSIDERATIONS
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The
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.Fn gets
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function cannot be used securely.
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Because of its lack of bounds checking,
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and the inability for the calling program
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to reliably determine the length of the next incoming line,
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the use of this function enables malicious users
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to arbitrarily change a running program's functionality through
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a buffer overflow attack.
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It is strongly suggested that the
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.Fn fgets
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function be used in all cases.
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