334 lines
10 KiB
Groff
334 lines
10 KiB
Groff
.\" $NetBSD: stdio.3,v 1.17 2003/01/28 20:26:04 kleink 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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.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" @(#)stdio.3 8.7 (Berkeley) 4/19/94
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.\"
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.Dd January 28, 2003
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.Dt STDIO 3
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.Os
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.Sh NAME
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.Nm stdio
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.Nd standard input/output library functions
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.Fd #include \*[Lt]stdio.h\*[Gt]
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.Fd FILE *stdin;
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.Fd FILE *stdout;
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.Fd FILE *stderr;
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.Sh DESCRIPTION
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The standard
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.Tn I/O
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library provides a simple and efficient buffered stream
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.Tn I/O
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interface.
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Input and output is mapped into logical data streams
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and the physical
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.Tn I/O
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characteristics are concealed.
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The functions and macros are listed below;
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more information is available from the individual man pages.
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.Pp
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A stream is associated with an external file (which may be a physical
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device) by
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.Em opening
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a file, which may involve creating a new file.
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Creating an existing file causes its former contents to be discarded.
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If a file can support positioning requests (such as a disk file, as opposed
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to a terminal) then a
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.Em file position indicator
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associated with the stream is positioned at the start of the file (byte
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zero), unless the file is opened with append mode.
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If append mode
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is used, the position indicator will be placed the end-of-file.
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The position indicator is maintained by subsequent reads, writes
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and positioning requests.
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All input occurs as if the characters
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were read by successive calls to the
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.Xr fgetc 3
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function; all output takes place as if all characters were
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read by successive calls to the
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.Xr fputc 3
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function.
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.Pp
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A file is disassociated from a stream by
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.Em closing
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the file.
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Output streams are flushed (any unwritten buffer contents are transferred
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to the host environment) before the stream is disassociated from the file.
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The value of a pointer to a
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.Dv FILE
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object is indeterminate after a file is closed (garbage).
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.Pp
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A file may be subsequently reopened, by the same or another program
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execution, and its contents reclaimed or modified (if it can be repositioned
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at the start).
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If the main function returns to its original caller, or the
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.Xr exit 3
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function is called, all open files are closed (hence all output
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streams are flushed) before program termination.
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Other methods of program termination, such as
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.Xr abort 3
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do not bother about closing files properly.
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.Pp
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This implementation needs and makes
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no distinction between
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.Dq text
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and
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.Dq binary
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streams.
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In effect, all streams are binary.
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No translation is performed and no extra padding appears on any stream.
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.Pp
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At program startup, three streams are predefined and need not be
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opened explicitly:
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.Bl -bullet -compact -offset indent
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.It
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.Em standard input
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(for reading conventional input),
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.It
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.Em standard output
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(for writing conventional output), and
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.It
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.Em standard error
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(for writing diagnostic output).
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.El
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These streams are abbreviated
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.Em stdin , stdout
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and
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.Em stderr .
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Initially, the standard error stream
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is unbuffered; the standard input and output streams are
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fully buffered if and only if the streams do not refer to
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an interactive or
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.Dq terminal
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device, as determined by the
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.Xr isatty 3
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function.
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In fact,
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.Em all
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freshly-opened streams that refer to terminal devices
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default to line buffering, and
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pending output to such streams is written automatically
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whenever an such an input stream is read.
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Note that this applies only to
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.Dq "true reads" ;
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if the read request can be satisfied by existing buffered data,
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no automatic flush will occur.
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In these cases,
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or when a large amount of computation is done after printing
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part of a line on an output terminal, it is necessary to
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.Xr fflush 3
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the standard output before going off and computing so that the output
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will appear.
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Alternatively, these defaults may be modified via the
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.Xr setvbuf 3
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function.
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.Pp
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The
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.Nm
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library is a part of the library
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.Pa libc.a
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and routines are automatically loaded as needed by compilers such
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as
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.Xr cc 1 .
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The
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.Tn SYNOPSIS
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sections of the following manual pages indicate which include files
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are to be used, what the compiler declaration for the function
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looks like and which external variables are of interest.
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.Pp
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In multi-threaded applications, operations on streams perform implicit
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locking, except for the
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.Fa getc_unlocked ,
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.Fa getchar_unlocked ,
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.Fa putc_unlocked ,
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and
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.Fa putchar_unlocked
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functions.
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Explicit control of stream locking is available through the
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.Fa flockfile ,
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.Fa ftrylockfile ,
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and
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.Fa funlockfile
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functions .
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.Pp
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The following are defined as macros; these names may not be re-used
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without first removing their current definitions with
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.Dv #undef :
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.Dv BUFSIZ ,
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.Dv EOF ,
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.Dv FILENAME_MAX ,
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.Dv FOPEN_MAX ,
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.Dv L_cuserid ,
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.Dv L_ctermid ,
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.Dv L_tmpnam ,
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.Dv NULL ,
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.Dv SEEK_END ,
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.Dv SEEK_SET ,
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.Dv SEE_CUR ,
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.Dv TMP_MAX ,
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.Fn clearerr ,
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.Fn feof ,
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.Fn ferror ,
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.Fn fileno ,
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.Fn freopen ,
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.Fn fwopen ,
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.Fn getc ,
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.Fn getc_unlocked ,
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.Fn getchar ,
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.Fn getchar_unlocked ,
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.Fn putc ,
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.Fn putc_unlocked ,
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.Fn putchar ,
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.Fn putchar_unlocked ,
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.Dv stderr ,
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.Dv stdin ,
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.Dv stdout .
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Function versions of the macro functions
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.Fn feof ,
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.Fn ferror ,
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.Fn clearerr ,
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.Fn fileno ,
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.Fn getc ,
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.Fn getc_unlocked ,
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.Fn getchar ,
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.Fn getchar_unlocked ,
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.Fn putc ,
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.Fn putc_unlocked ,
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.Fn putchar ,
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and
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.Fn putchar_unlocked
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exist and will be used if the macros definitions are explicitly removed.
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.Sh SEE ALSO
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.Xr close 2 ,
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.Xr open 2 ,
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.Xr read 2 ,
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.Xr write 2
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.Sh STANDARDS
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The
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.Nm
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library conforms to
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.St -ansiC .
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.Sh LIST OF FUNCTIONS
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.Bl -column "Functionxxxxxxxx" "Description"
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.Sy Function Description
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clearerr check and reset stream status
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fclose close a stream
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fdopen stream open functions
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feof check and reset stream status
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ferror check and reset stream status
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fflush flush a stream
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fgetc get next character or word from input stream
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fgetln get a line from a stream
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fgetpos reposition a stream
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fgets get a line from a stream
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fgetwc get next wide character from input stream
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fileno check and reset stream status
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flockfile lock a stream
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fopen stream open functions
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fprintf formatted output conversion
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fpurge flush a stream
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fputc output a character or word to a stream
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fputs output a line to a stream
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fputwc output a wide character to a stream
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fread binary stream input/output
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freopen stream open functions
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fropen open a stream
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fscanf input format conversion
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fseek reposition a stream
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fsetpos reposition a stream
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ftell reposition a stream
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ftrylockfile lock a stream (non-blocking)
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funlockfile unlock a stream
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funopen open a stream
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fwide set/get orientation of a stream
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fwopen open a stream
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fwrite binary stream input/output
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getc get next character or word from input stream
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getc_unlocked get next character or word from input stream
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(no implicit locking)
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getchar get next character or word from input stream
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getchar_unlocked get next character or word from input stream
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(no implicit locking)
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gets get a line from a stream
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getw get next character or word from input stream
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getwc get next wide character from input stream
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getwchar get next wide character from input stream
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mkstemp create unique temporary file
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mktemp create unique temporary file
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perror system error messages
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printf formatted output conversion
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putc output a character or word to a stream
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putc_unlocked output a character or word to a stream
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(no implicit locking)
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putchar output a character or word to a stream
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putchar_unlocked output a character or word to a stream
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(no implicit locking)
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puts output a line to a stream
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putw output a character or word to a stream
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putwc output a wide character to a stream
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putwchar output a wide character to a stream
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remove remove directory entry
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rewind reposition a stream
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scanf input format conversion
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setbuf stream buffering operations
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setbuffer stream buffering operations
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setlinebuf stream buffering operations
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setvbuf stream buffering operations
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snprintf formatted output conversion
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sprintf formatted output conversion
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sscanf input format conversion
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strerror system error messages
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sys_errlist system error messages
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sys_nerr system error messages
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tempnam temporary file routines
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tmpfile temporary file routines
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tmpnam temporary file routines
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ungetc un-get character from input stream
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ungetwc un-get wide character from input stream
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vfprintf formatted output conversion
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vfscanf input format conversion
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vprintf formatted output conversion
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vscanf input format conversion
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vsnprintf formatted output conversion
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vsprintf formatted output conversion
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vsscanf input format conversion
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.El
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.Sh BUGS
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The standard buffered functions do not interact well with certain other
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library and system functions, especially
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.Xr vfork 2
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and
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.Xr abort 3 .
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