2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
201 lines
5.1 KiB
Groff
201 lines
5.1 KiB
Groff
.\" $NetBSD: fgets.3,v 1.22 2010/05/13 18:38:24 jruoho Exp $
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.\"
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.\" 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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.\"
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.Dd May 13, 2010
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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, and 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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.Em 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 or an error occurs before any characters are read,
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they return
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.Dv NULL .
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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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.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 -ansiC
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and
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.St -p1003.1-2001 .
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The
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.St -p1003.1-2008
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revision marked
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.Fn gets
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as obsolescent.
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.Sh CAVEATS
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The following bit of code illustrates a case where the programmer assumes a
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string is too long if it does not contain a newline:
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.Bd -literal
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char buf[1024], *p;
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while (fgets(buf, sizeof(buf), fp) != NULL) {
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if ((p = strchr(buf, '\en')) == NULL) {
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fprintf(stderr, "input line too long.\en");
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exit(1);
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}
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*p = '\e0';
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printf("%s\en", buf);
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}
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.Ed
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.Pp
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While the error would be true if a line longer than 1023 characters
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were read, it would be false in two other cases:
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.Bl -enum -offset indent
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.It
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If the last line in a file does not contain a newline, the string returned by
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.Fn fgets
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will not contain a newline either.
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Thus
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.Fn strchr
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will return
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.Dv NULL
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and the program will terminate, even if the line was valid.
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.It
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All C string functions, including
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.Fn strchr ,
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correctly assume the end of the string is represented by a null
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.Pq Sq \e0
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character.
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If the first character of a line returned by
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.Fn fgets
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were null,
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.Fn strchr
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would immediately return without considering the rest of the returned text
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which may indeed include a newline.
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.El
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.Pp
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Consider using
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.Xr fgetln 3
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instead when dealing with untrusted input.
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.Sh SECURITY CONSIDERATIONS
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Since it is usually impossible to ensure that the next input line
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is less than some arbitrary length, and because overflowing the
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input buffer is almost invariably a security violation, programs
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should
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.Em NEVER
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use
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.Fn gets .
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The
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.Fn gets
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function
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exists purely to conform to
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.St -ansiC .
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