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430 lines
11 KiB
Groff
430 lines
11 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. 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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.\" @(#)scanf.3 8.2 (Berkeley) 12/11/93
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.\"
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.TH SCANF 3 "15 September 1997" GNO "Library Routines"
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.SH NAME
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.BR scanf ,
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.BR fscanf ,
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.BR sscanf ,
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.BR vscanf ,
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.BR vsscanf ,
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.BR vfscanf
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\- input format conversion
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.SH SYNOPSIS
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#include <stdio.h>
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.sp 1
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int \fBscanf\fR (const char *\fIformat\fR, ...);
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.br
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int \fBfscanf\fR (FILE *\fIstream\fR, const char *\fIformat\fR, ...);
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.br
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int \fBsscanf\fR (const char *\fIstr\fR, const char *\fIformat\fR, ...);
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.sp 1
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#include <stdarg.h>
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.sp 1
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int \fBvscanf\fR (const char *\fIformat\fR, va_list \fIap\fR);
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.br
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int \fBvsscanf\fR (const char *\fIstr\fR, const char *\fIformat\fR, va_list \fIap\fR);
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.br
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int \fBvfscanf\fR (FILE *\fIstream\fR, const char *\fIformat\fR, va_list \fIap\fR);
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.SH DESCRIPTION
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The
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.BR scanf
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family of functions scans input according to a
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.I format
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as described below.
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This format may contain
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.IR "conversion specifiers" ;
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the results from such conversions, if any,
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are stored through the
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.IR pointer
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arguments.
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.LP
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The
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.BR scanf
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function
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reads input from the standard input stream
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.IR stdin ,
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.BR fscanf
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reads input from the stream pointer
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.IR stream ,
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and
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.BR sscanf
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reads its input from the character string pointed to by
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.IR str .
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The
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.BR vfscanf
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function
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is analogous to
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.BR vfprintf (3)
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and reads input from the stream pointer
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.I stream
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using a variable argument list of pointers (see
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.BR stdarg (3)).
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The
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.BR vscanf
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function scans a variable argument list from the standard input and
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the
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.BR vsscanf
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function scans it from a string;
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these are analogous to
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the
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.BR vprintf
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and
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.BR vsprintf
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functions respectively.
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.LP
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Each successive
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.IR pointer
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argument must correspond properly with
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each successive conversion specifier
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(but see `suppression' below).
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All conversions are introduced by the
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.BR %
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(percent sign) character.
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The
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.I format
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string
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may also contain other characters.
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White space (such as blanks, tabs, or newlines) in the
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.I format
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string match any amount of white space, including none, in the input.
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Everything else
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matches only itself.
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Scanning stops
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when an input character does not match such a format character.
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Scanning also stops
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when an input conversion cannot be made (see below).
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.SH CONVERSIONS
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Following the
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.BR %
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character introducing a conversion
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there may be a number of
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.IR flag
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characters, as follows:
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.RS
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.IP \fB*\fR
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Suppresses assignment.
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The conversion that follows occurs as usual, but no pointer is used;
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the result of the conversion is simply discarded.
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.IP \fBh\fR
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Indicates that the conversion will be one of
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.BR dioux
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or
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.BR n
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and the next pointer is a pointer to a
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.IR "short int"
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(rather than
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.IR int ).
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.IP \fBl\fR
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Indicates either that the conversion will be one of
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.BR dioux
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or
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.BR n
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and the next pointer is a pointer to a
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.IR "long int"
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(rather than
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.IR int ),
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or that the conversion will be one of
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.BR efg
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and the next pointer is a pointer to
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.IR double
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(rather than
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.IR float ).
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.IP \fBL\fR
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Indicates that the conversion will be
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.BR efg
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and the next pointer is a pointer to
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.IR "long double" .
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(This type is not implemented; the
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.BR L
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flag is currently ignored.)
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.RE
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.LP
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In addition to these flags,
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there may be an optional maximum field width,
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expressed as a decimal integer,
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between the
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.BR %
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and the conversion.
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If no width is given,
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a default of `infinity' is used (with one exception, below);
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otherwise at most this many characters are scanned
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in processing the conversion.
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Before conversion begins,
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most conversions skip white space;
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this white space is not counted against the field width.
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.LP
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The following conversions are available:
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.RS
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.IP \fB%\fR
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Matches a literal `%'.
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That is, `%\&%' in the format string
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matches a single input `%' character.
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No conversion is done, and assignment does not occur.
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.IP \fBd\fR
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Matches an optionally signed decimal integer;
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the next pointer must be a pointer to
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.IR int .
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.IP \fBD\fR
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Equivalent to
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.BR ld ;
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this exists only for backwards compatibility.
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.IP \fBi\fR
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Matches an optionally signed integer;
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the next pointer must be a pointer to
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.IR int .
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The integer is read in base 16 if it begins
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with
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.BR 0x
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or
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.BR 0X ,
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in base 8 if it begins with
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.BR 0 ,
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and in base 10 otherwise.
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Only characters that correspond to the base are used.
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.IP \fBo\fR
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Matches an octal integer;
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the next pointer must be a pointer to
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.IR "unsigned int" .
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.IP \fBO\fR
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Equivalent to
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.BR lo ;
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this exists for backwards compatibility.
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.IP \fBu\fR
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Matches an optionally signed decimal integer;
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the next pointer must be a pointer to
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.IR "unsigned int" .
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.IP \fBx\fR
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Matches an optionally signed hexadecimal integer;
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the next pointer must be a pointer to
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.IR "unsigned int" .
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.IP \fBX\fR
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Equivalent to
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.BR lx ;
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this violates the ANSI/C standard,
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but is backwards compatible with previous
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UNIX systems.
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.IP \fBf\fR
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Matches an optionally signed floating-point number;
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the next pointer must be a pointer to
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.IR float .
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.IP \fBe\fR
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Equivalent to
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.BR f .
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.IP \fBg\fR
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Equivalent to
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.BR f .
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.IP \fBE\fR
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Equivalent to
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.BR lf ;
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this violates the ANSI/C standard,
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but is backwards compatible with previous
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UNIX systems.
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.IP \fBF\fR
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Equivalent to
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.BR lf ;
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this exists only for backwards compatibility.
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.IP \fBs\fR
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Matches a sequence of non-white-space characters;
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the next pointer must be a pointer to
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.IR char ,
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and the array must be large enough to accept all the sequence and the
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terminating
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.BR NUL
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character.
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The input string stops at white space
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or at the maximum field width, whichever occurs first.
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.IP \fBc\fR
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Matches a sequence of
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.IR width
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count
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characters (default 1);
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the next pointer must be a pointer to
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.IR char ,
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and there must be enough room for all the characters
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(no terminating
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.BR NUL
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is added).
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The usual skip of leading white space is suppressed.
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To skip white space first, use an explicit space in the format.
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.IP \fB\&[\fR
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Matches a nonempty sequence of characters from the specified set
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of accepted characters;
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the next pointer must be a pointer to
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.IR char ,
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and there must be enough room for all the characters in the string,
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plus a terminating
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.BR NUL
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character.
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The usual skip of leading white space is suppressed.
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The string is to be made up of characters in
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(or not in)
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a particular set;
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the set is defined by the characters between the open bracket
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.BR [
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character
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and a close bracket
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.BR ]
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character.
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The set
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.IR excludes
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those characters
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if the first character after the open bracket is a circumflex
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.BR ^ .
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To include a close bracket in the set,
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make it the first character after the open bracket
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or the circumflex;
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any other position will end the set.
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The hyphen character
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.BR -
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is also special;
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when placed between two other characters,
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it adds all intervening characters to the set.
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To include a hyphen,
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make it the last character before the final close bracket.
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For instance,
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.BR [^]0-9-]
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means the set `everything except close bracket, zero through nine,
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and hyphen'.
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The string ends with the appearance of a character not in the
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(or, with a circumflex, in) set
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or when the field width runs out.
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.IP \fBp\fR
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Matches a pointer value (as printed by
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.BR %p
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in
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.BR printf (3));
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the next pointer must be a pointer to
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.IR void .
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.IP \fBn\fR
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Nothing is expected;
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instead, the number of characters consumed thus far from the input
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is stored through the next pointer,
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which must be a pointer to
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.IR int .
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This is
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.IR not
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a conversion, although it can be suppressed with the
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.BR *
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flag.
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.RE
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.LP
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For backwards compatibility,
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other conversion characters (except
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.BR \e0 )
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are taken as if they were
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.BR %d
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or, if uppercase,
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.BR %ld ,
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and a `conversion' of
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.BR %\e0
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causes an immediate return of
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.BR EOF .
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The
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.BR F
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and
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.BR X
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conversions will be changed in the future
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to conform to the ANSI/C standard,
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after which they will act like
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.BR f
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and
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.BR x
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respectively.
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.LP
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.SH RETURN VALUES
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These
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functions
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return
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the number of input items assigned, which can be fewer than provided
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for, or even zero, in the event of a matching failure.
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Zero
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indicates that, while there was input available,
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no conversions were assigned;
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typically this is due to an invalid input character,
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such as an alphabetic character for a
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.BR %d
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conversion.
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.LP
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The value
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.BR EOF
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is returned if an input failure occurs before any conversion such as an
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end-of-file occurs. If an error or end-of-file occurs after conversion
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has begun,
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the number of conversions which were successfully completed is returned.
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.SH SEE ALSO
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.BR strtol (3),
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.BR strtoul (3),
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.BR strtod (3),
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.BR getc (3),
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.BR printf (3)
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.SH STANDARDS
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The functions
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.BR fscanf ,
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.BR scanf ,
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and
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.BR sscanf
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conform to ANSI/C.
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.SH HISTORY
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The functions
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.BR vscanf ,
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.BR vsscanf
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and
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.BR vfscanf
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are new to this release.
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.SH BUGS
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The ORCA/C stdio implementation also provides a
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.BR %b
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format specifier, for Pascal-type strings. This is not currently implemented.
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.LP
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The current situation with
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.BR %F
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and
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.BR %X
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conversions is unfortunate.
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.LP
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All of the backwards compatibility formats will be removed in the future.
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.LP
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Numerical strings are truncated to 512 characters; for example,
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.BR %f
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and
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.BR %d
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are implicitly
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.BR %512f
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and
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.BR %512d .
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