73129d4797
PR: 240269 Submitted by: Gordon Bergling Differential Revision: https://reviews.freebsd.org/D24295
186 lines
4.4 KiB
Groff
186 lines
4.4 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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.\" @(#)getc.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd April 4, 2020
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.Dt GETC 3
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.Os
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.Sh NAME
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.Nm fgetc ,
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.Nm getc ,
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.Nm getc_unlocked ,
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.Nm getchar ,
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.Nm getchar_unlocked ,
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.Nm getw
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.Nd get next character or word from input 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 int
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.Fn fgetc "FILE *stream"
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.Ft int
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.Fn getc "FILE *stream"
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.Ft int
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.Fn getc_unlocked "FILE *stream"
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.Ft int
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.Fn getchar void
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.Ft int
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.Fn getchar_unlocked void
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.Ft int
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.Fn getw "FILE *stream"
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.Sh DESCRIPTION
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The
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.Fn fgetc
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function
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obtains the next input character (if present) from the stream pointed at by
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.Fa stream ,
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or the next character pushed back on the stream via
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.Xr ungetc 3 .
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.Pp
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The
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.Fn getc
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function
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acts essentially identically to
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.Fn fgetc ,
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but is a macro that expands in-line.
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.Pp
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The
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.Fn getchar
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function
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is equivalent to
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.Fn getc stdin .
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.Pp
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The
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.Fn getw
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function
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obtains the next
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.Vt int
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(if present)
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from the stream pointed at by
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.Fa stream .
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.Pp
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The
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.Fn getc_unlocked
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and
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.Fn getchar_unlocked
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functions are equivalent to
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.Fn getc
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and
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.Fn getchar
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respectively,
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except that the caller is responsible for locking the stream
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with
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.Xr flockfile 3
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before calling them.
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These functions may be used to avoid the overhead of locking the stream
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for each character, and to avoid input being dispersed among multiple
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threads reading from the same stream.
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.Sh RETURN VALUES
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If successful, these routines return the next requested object
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from the
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.Fa stream .
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Character values are returned as an
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.Vt "unsigned char"
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converted to an
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.Vt int .
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If the stream is at end-of-file or a read error occurs,
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the routines return
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.Dv EOF .
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The routines
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.Xr feof 3
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and
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.Xr ferror 3
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must be used to distinguish between end-of-file and error.
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If an error occurs, the global variable
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.Va errno
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is set to indicate the error.
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The end-of-file condition is remembered, even on a terminal, and all
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subsequent attempts to read will return
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.Dv EOF
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until the condition is cleared with
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.Xr clearerr 3 .
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.Sh SEE ALSO
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.Xr ferror 3 ,
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.Xr flockfile 3 ,
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.Xr fopen 3 ,
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.Xr fread 3 ,
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.Xr getwc 3 ,
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.Xr putc 3 ,
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.Xr ungetc 3
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.Sh STANDARDS
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The
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.Fn fgetc ,
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.Fn getc ,
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and
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.Fn getchar
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functions
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conform to
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.St -isoC .
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The
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.Fn getc_unlocked
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and
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.Fn getchar_unlocked
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functions conform to
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.St -p1003.1-2001 .
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.Sh HISTORY
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The
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.Fn getc
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and
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.Fn getw
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functions appeared in a similar form in
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.At v1 ;
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and were integrated into stdio in
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.At v7 ;
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.Fn getchar
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in
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.At v4 ;
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and
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.Fn fgetc
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in
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.At v7 .
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.Sh BUGS
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Since
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.Dv EOF
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is a valid integer value,
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.Xr feof 3
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and
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.Xr ferror 3
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must be used to check for failure after calling
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.Fn getw .
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The size and byte order of an
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.Vt int
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varies from one machine to another, and
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.Fn getw
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is not recommended for portable applications.
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