444 lines
11 KiB
Groff
444 lines
11 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
.\" Chris Torek and the American National Standards Committee X3,
|
|
.\" on Information Processing Systems.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)scanf.3 8.2 (Berkeley) 12/11/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 11, 1993
|
|
.Dt SCANF 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm scanf ,
|
|
.Nm fscanf ,
|
|
.Nm sscanf ,
|
|
.Nm vscanf ,
|
|
.Nm vsscanf ,
|
|
.Nm vfscanf
|
|
.Nd input format conversion
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.Fd #include <stdio.h>
|
|
.Ft int
|
|
.Fn scanf "const char *format" ...
|
|
.Ft int
|
|
.Fn fscanf "FILE *stream" "const char *format" ...
|
|
.Ft int
|
|
.Fn sscanf "const char *str" "const char *format" ...
|
|
.Fd #include <stdarg.h>
|
|
.Ft int
|
|
.Fn vscanf "const char *format" "va_list ap"
|
|
.Ft int
|
|
.Fn vsscanf "const char *str" "const char *format" "va_list ap"
|
|
.Ft int
|
|
.Fn vfscanf "FILE *stream" "const char *format" "va_list ap"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn scanf
|
|
family of functions scans input according to a
|
|
.Fa format
|
|
as described below.
|
|
This format may contain
|
|
.Em conversion specifiers ;
|
|
the results from such conversions, if any,
|
|
are stored through the
|
|
.Em pointer
|
|
arguments.
|
|
The
|
|
.Fn scanf
|
|
function
|
|
reads input from the standard input stream
|
|
.Em stdin ,
|
|
.Fn fscanf
|
|
reads input from the stream pointer
|
|
.Fa stream ,
|
|
and
|
|
.Fn sscanf
|
|
reads its input from the character string pointed to by
|
|
.Fa str .
|
|
The
|
|
.Fn vfscanf
|
|
function
|
|
is analogous to
|
|
.Xr vfprintf 3
|
|
and reads input from the stream pointer
|
|
.Fa stream
|
|
using a variable argument list of pointers (see
|
|
.Xr stdarg 3 ) .
|
|
The
|
|
.Fn vscanf
|
|
function scans a variable argument list from the standard input and
|
|
the
|
|
.Fn vsscanf
|
|
function scans it from a string;
|
|
these are analogous to
|
|
the
|
|
.Fn vprintf
|
|
and
|
|
.Fn vsprintf
|
|
functions respectively.
|
|
Each successive
|
|
.Em pointer
|
|
argument must correspond properly with
|
|
each successive conversion specifier
|
|
(but see `suppression' below).
|
|
All conversions are introduced by the
|
|
.Cm %
|
|
(percent sign) character.
|
|
The
|
|
.Fa format
|
|
string
|
|
may also contain other characters.
|
|
White space (such as blanks, tabs, or newlines) in the
|
|
.Fa format
|
|
string match any amount of white space, including none, in the input.
|
|
Everything else
|
|
matches only itself.
|
|
Scanning stops
|
|
when an input character does not match such a format character.
|
|
Scanning also stops
|
|
when an input conversion cannot be made (see below).
|
|
.Sh CONVERSIONS
|
|
Following the
|
|
.Cm %
|
|
character introducing a conversion
|
|
there may be a number of
|
|
.Em flag
|
|
characters, as follows:
|
|
.Bl -tag -width indent
|
|
.It Cm *
|
|
Suppresses assignment.
|
|
The conversion that follows occurs as usual, but no pointer is used;
|
|
the result of the conversion is simply discarded.
|
|
.It Cm h
|
|
Indicates that the conversion will be one of
|
|
.Cm dioux
|
|
or
|
|
.Cm n
|
|
and the next pointer is a pointer to a
|
|
.Em short int
|
|
(rather than
|
|
.Em int ) .
|
|
.It Cm l
|
|
Indicates either that the conversion will be one of
|
|
.Cm dioux
|
|
or
|
|
.Cm n
|
|
and the next pointer is a pointer to a
|
|
.Em long int
|
|
(rather than
|
|
.Em int ) ,
|
|
or that the conversion will be one of
|
|
.Cm efg
|
|
and the next pointer is a pointer to
|
|
.Em double
|
|
(rather than
|
|
.Em float ) .
|
|
.It Cm L
|
|
Indicates that the conversion will be
|
|
.Cm efg
|
|
and the next pointer is a pointer to
|
|
.Em long double .
|
|
(This type is not implemented; the
|
|
.Cm L
|
|
flag is currently ignored.)
|
|
.It Cm q
|
|
Indicates either that the conversion will be one of
|
|
.Cm dioux
|
|
or
|
|
.Cm n
|
|
and the next pointer is a pointer to a
|
|
.Em long long int
|
|
(rather than
|
|
.Em int ) ,
|
|
.El
|
|
.Pp
|
|
In addition to these flags,
|
|
there may be an optional maximum field width,
|
|
expressed as a decimal integer,
|
|
between the
|
|
.Cm %
|
|
and the conversion.
|
|
If no width is given,
|
|
a default of `infinity' is used (with one exception, below);
|
|
otherwise at most this many characters are scanned
|
|
in processing the conversion.
|
|
Before conversion begins,
|
|
most conversions skip white space;
|
|
this white space is not counted against the field width.
|
|
.Pp
|
|
The following conversions are available:
|
|
.Bl -tag -width XXXX
|
|
.It Cm %
|
|
Matches a literal `%'.
|
|
That is, `%\&%' in the format string
|
|
matches a single input `%' character.
|
|
No conversion is done, and assignment does not occur.
|
|
.It Cm d
|
|
Matches an optionally signed decimal integer;
|
|
the next pointer must be a pointer to
|
|
.Em int .
|
|
.It Cm D
|
|
Equivalent to
|
|
.Cm ld ;
|
|
this exists only for backwards compatibility.
|
|
.It Cm i
|
|
Matches an optionally signed integer;
|
|
the next pointer must be a pointer to
|
|
.Em int .
|
|
The integer is read in base 16 if it begins
|
|
with
|
|
.Ql 0x
|
|
or
|
|
.Ql 0X ,
|
|
in base 8 if it begins with
|
|
.Ql 0 ,
|
|
and in base 10 otherwise.
|
|
Only characters that correspond to the base are used.
|
|
.It Cm o
|
|
Matches an octal integer;
|
|
the next pointer must be a pointer to
|
|
.Em unsigned int .
|
|
.It Cm O
|
|
Equivalent to
|
|
.Cm lo ;
|
|
this exists for backwards compatibility.
|
|
.It Cm u
|
|
Matches an optionally signed decimal integer;
|
|
the next pointer must be a pointer to
|
|
.Em unsigned int .
|
|
.It Cm x
|
|
Matches an optionally signed hexadecimal integer;
|
|
the next pointer must be a pointer to
|
|
.Em unsigned int .
|
|
.It Cm X
|
|
Equivalent to
|
|
.Cm lx ;
|
|
this violates the
|
|
.St -ansiC ,
|
|
but is backwards compatible with previous
|
|
.Ux
|
|
systems.
|
|
.It Cm f
|
|
Matches an optionally signed floating-point number;
|
|
the next pointer must be a pointer to
|
|
.Em float .
|
|
.It Cm e
|
|
Equivalent to
|
|
.Cm f .
|
|
.It Cm g
|
|
Equivalent to
|
|
.Cm f .
|
|
.It Cm E
|
|
Equivalent to
|
|
.Cm lf ;
|
|
this violates the
|
|
.St -ansiC ,
|
|
but is backwards compatible with previous
|
|
.Ux
|
|
systems.
|
|
.It Cm F
|
|
Equivalent to
|
|
.Cm lf ;
|
|
this exists only for backwards compatibility.
|
|
.It Cm s
|
|
Matches a sequence of non-white-space characters;
|
|
the next pointer must be a pointer to
|
|
.Em char ,
|
|
and the array must be large enough to accept all the sequence and the
|
|
terminating
|
|
.Dv NUL
|
|
character.
|
|
The input string stops at white space
|
|
or at the maximum field width, whichever occurs first.
|
|
.It Cm c
|
|
Matches a sequence of
|
|
.Em width
|
|
count
|
|
characters (default 1);
|
|
the next pointer must be a pointer to
|
|
.Em char ,
|
|
and there must be enough room for all the characters
|
|
(no terminating
|
|
.Dv NUL
|
|
is added).
|
|
The usual skip of leading white space is suppressed.
|
|
To skip white space first, use an explicit space in the format.
|
|
.It Cm \&[
|
|
Matches a nonempty sequence of characters from the specified set
|
|
of accepted characters;
|
|
the next pointer must be a pointer to
|
|
.Em char ,
|
|
and there must be enough room for all the characters in the string,
|
|
plus a terminating
|
|
.Dv NUL
|
|
character.
|
|
The usual skip of leading white space is suppressed.
|
|
The string is to be made up of characters in
|
|
(or not in)
|
|
a particular set;
|
|
the set is defined by the characters between the open bracket
|
|
.Cm [
|
|
character
|
|
and a close bracket
|
|
.Cm ]
|
|
character.
|
|
The set
|
|
.Em excludes
|
|
those characters
|
|
if the first character after the open bracket is a circumflex
|
|
.Cm ^ .
|
|
To include a close bracket in the set,
|
|
make it the first character after the open bracket
|
|
or the circumflex;
|
|
any other position will end the set.
|
|
The hyphen character
|
|
.Cm -
|
|
is also special;
|
|
when placed between two other characters,
|
|
it adds all intervening characters to the set.
|
|
To include a hyphen,
|
|
make it the last character before the final close bracket.
|
|
For instance,
|
|
.Ql [^]0-9-]
|
|
means the set `everything except close bracket, zero through nine,
|
|
and hyphen'.
|
|
The string ends with the appearance of a character not in the
|
|
(or, with a circumflex, in) set
|
|
or when the field width runs out.
|
|
.It Cm p
|
|
Matches a pointer value (as printed by
|
|
.Ql %p
|
|
in
|
|
.Xr printf 3 ) ;
|
|
the next pointer must be a pointer to
|
|
.Em void .
|
|
.It Cm n
|
|
Nothing is expected;
|
|
instead, the number of characters consumed thus far from the input
|
|
is stored through the next pointer,
|
|
which must be a pointer to
|
|
.Em int .
|
|
This is
|
|
.Em not
|
|
a conversion, although it can be suppressed with the
|
|
.Cm *
|
|
flag.
|
|
.El
|
|
.Pp
|
|
For backwards compatibility,
|
|
other conversion characters (except
|
|
.Ql \e0 )
|
|
are taken as if they were
|
|
.Ql %d
|
|
or, if uppercase,
|
|
.Ql %ld ,
|
|
and a `conversion' of
|
|
.Ql %\e0
|
|
causes an immediate return of
|
|
.Dv EOF .
|
|
The
|
|
.Cm F
|
|
and
|
|
.Cm X
|
|
conversions will be changed in the future
|
|
to conform to the
|
|
.Tn ANSI
|
|
C standard,
|
|
after which they will act like
|
|
.Cm f
|
|
and
|
|
.Cm x
|
|
respectively.
|
|
.Pp
|
|
.Sh RETURN VALUES
|
|
These
|
|
functions
|
|
return
|
|
the number of input items assigned, which can be fewer than provided
|
|
for, or even zero, in the event of a matching failure.
|
|
Zero
|
|
indicates that, while there was input available,
|
|
no conversions were assigned;
|
|
typically this is due to an invalid input character,
|
|
such as an alphabetic character for a
|
|
.Ql %d
|
|
conversion.
|
|
The value
|
|
.Dv EOF
|
|
is returned if an input failure occurs before any conversion such as an
|
|
end-of-file occurs.
|
|
If an error or end-of-file occurs after conversion
|
|
has begun,
|
|
the number of conversions which were successfully completed is returned.
|
|
.Sh SEE ALSO
|
|
.Xr getc 3 ,
|
|
.Xr printf 3 ,
|
|
.Xr strtod 3 ,
|
|
.Xr strtol 3 ,
|
|
.Xr strtoul 3
|
|
.Sh STANDARDS
|
|
The functions
|
|
.Fn fscanf ,
|
|
.Fn scanf ,
|
|
and
|
|
.Fn sscanf
|
|
conform to
|
|
.St -ansiC .
|
|
.Sh HISTORY
|
|
The functions
|
|
.Fn vscanf ,
|
|
.Fn vsscanf
|
|
and
|
|
.Fn vfscanf
|
|
are new to this release.
|
|
.Sh BUGS
|
|
The current situation with
|
|
.Cm %F
|
|
and
|
|
.Cm %X
|
|
conversions is unfortunate.
|
|
.Pp
|
|
All of the backwards compatibility formats will be removed in the future.
|
|
.Pp
|
|
Numerical strings are truncated to 512 characters; for example,
|
|
.Cm %f
|
|
and
|
|
.Cm %d
|
|
are implicitly
|
|
.Cm %512f
|
|
and
|
|
.Cm %512d .
|