309 lines
10 KiB
Groff
309 lines
10 KiB
Groff
.\" $OpenBSD: stdio.3,v 1.31 2014/07/03 06:08:06 jmc 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. 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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.Dd $Mdocdate: July 3 2014 $
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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 SYNOPSIS
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.In stdio.h
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.Pp
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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 I/O library
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provides a simple and efficient buffered stream I/O interface.
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Input and output is mapped into logical data streams and the physical 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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.Dq 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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.Dq 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 at 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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written 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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.Dq closing
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it.
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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 (garbage) after a file is closed.
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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 may not close files properly and hence
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buffered output may be lost.
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In particular,
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.Xr _exit 2
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does not flush
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.Nm
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files.
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Neither does an exit due to a signal.
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Buffers are flushed by
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.Xr abort 3 ,
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as required by POSIX, although in previous implementations they were not.
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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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.Pp
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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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.Pp
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These streams are abbreviated
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.Em stdin ,
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.Em 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 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 so that the output will appear immediately.
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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 stdio
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library is a part of the library libc
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and routines are automatically loaded as needed by the compiler.
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The 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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The following are defined as macros;
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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_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 SEEK_CUR ,
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.Dv TMP_MAX ,
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.Dv clearerr ,
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.Dv feof ,
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.Dv ferror ,
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.Dv fileno ,
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.Dv freopen ,
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.Dv fwopen ,
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.Dv getc ,
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.Dv getchar ,
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.Dv putc ,
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.Dv putchar ,
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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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.Xr feof 3 ,
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.Xr ferror 3 ,
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.Xr clearerr 3 ,
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.Xr fileno 3 ,
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.Xr getc 3 ,
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.Xr getchar 3 ,
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.Xr putc 3 ,
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and
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.Xr putchar 3
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exist and will be used if the macro
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definitions are explicitly removed.
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.Sh LIST OF FUNCTIONS
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.Bl -column "sys_errlist" "Description"
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.It Sy Function Ta Sy Description
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.It asprintf Ta "formatted output conversion with allocation"
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.It clearerr Ta "check and reset stream status"
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.It dprintf Ta "formatted output conversion"
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.It fclose Ta "close a stream"
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.It fdopen Ta "stream open functions"
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.It feof Ta "check and reset stream status"
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.It ferror Ta "check and reset stream status"
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.It fflush Ta "flush a stream"
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.It fgetc Ta "get next character or word from input stream"
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.It fgetln Ta "get a line from a stream"
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.It fgetpos Ta "reposition a stream"
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.It fgets Ta "get a line from a stream"
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.It fgetwc Ta "get next wide character from input stream"
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.It fgetws Ta "get a line of wide characters from a stream"
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.It fileno Ta "get a stream's underlying file descriptor"
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.It fopen Ta "stream open functions"
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.It fprintf Ta "formatted output conversion"
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.It fpurge Ta "flush a stream"
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.It fputc Ta "output a character or word to a stream"
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.It fputs Ta "output a line to a stream"
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.It fputwc Ta "output a wide character to a stream"
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.It fputws Ta "output a line of wide characters to a stream"
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.It fread Ta "binary stream input/output"
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.It freopen Ta "stream open functions"
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.It fropen Ta "open a stream"
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.It fscanf Ta "input format conversion"
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.It fseek Ta "reposition a stream"
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.It fsetpos Ta "reposition a stream"
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.It ftell Ta "reposition a stream"
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.It funopen Ta "open a stream"
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.It fwide Ta "set/get orientation of stream"
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.It fwopen Ta "open a stream"
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.It fwprintf Ta "formatted wide character output conversion"
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.It fwrite Ta "binary stream input/output"
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.It getc Ta "get next character or word from input stream"
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.It getchar Ta "get next character or word from input stream"
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.It getdelim Ta "read a delimited record from a stream"
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.It getline Ta "read a delimited record from a stream"
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.It getw Ta "get next character or word from input stream"
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.It getwc Ta "get next wide character from input stream"
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.It getwchar Ta "get next wide character from input stream"
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.It mkdtemp Ta "create unique temporary directory"
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.It mkstemp Ta "create unique temporary file"
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.It mktemp Ta "create unique temporary file"
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.It perror Ta "system error messages"
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.It printf Ta "formatted output conversion"
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.It putc Ta "output a character or word to a stream"
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.It putchar Ta "output a character or word to a stream"
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.It puts Ta "output a line to a stream"
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.It putw Ta "output a character or word to a stream"
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.It putwc Ta "output a wide character to a stream"
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.It putwchar Ta "output a wide character to a stream"
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.It remove Ta "remove directory entry"
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.It rewind Ta "reposition a stream"
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.It scanf Ta "input format conversion"
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.It setbuf Ta "stream buffering operations"
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.It setbuffer Ta "stream buffering operations"
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.It setlinebuf Ta "stream buffering operations"
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.It setvbuf Ta "stream buffering operations"
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.It snprintf Ta "formatted output conversion"
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.It sprintf Ta "formatted output conversion"
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.It sscanf Ta "input format conversion"
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.It strerror Ta "system error messages"
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.It swprintf Ta "formatted wide character output conversion"
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.It sys_errlist Ta "system error messages"
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.It sys_nerr Ta "system error messages"
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.It tempnam Ta "temporary file routines"
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.It tmpfile Ta "temporary file routines"
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.It tmpnam Ta "temporary file routines"
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.It ungetc Ta "un-get character from input stream"
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.It ungetwc Ta "un-get wide character from input stream"
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.It vasprintf Ta "formatted output conversion with allocation"
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.It vdprintf Ta "formatted output conversion"
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.It vfprintf Ta "formatted output conversion"
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.It vfscanf Ta "input format conversion"
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.It vfwprintf Ta "formatted wide character output conversion"
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.It vprintf Ta "formatted output conversion"
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.It vscanf Ta "input format conversion"
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.It vsnprintf Ta "formatted output conversion"
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.It vsprintf Ta "formatted output conversion"
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.It vsscanf Ta "input format conversion"
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.It vswprintf Ta "formatted wide character output conversion"
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.It vwprintf Ta "formatted wide character output conversion"
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.It wprintf Ta "formatted wide character output conversion"
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.El
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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 stdio
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library conforms to
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.St -isoC-99 .
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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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