'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\" Copyright (c) 2000 Scriptics Corporation.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: scan.n,v 1.14 2003/03/19 23:01:13 cagney Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
'\"	or "in/out" to describe whether procedure reads or modifies arg,
'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"	Give maximum sizes of arguments for setting tab stops.  Type and
'\"	name are examples of largest possible arguments that will be passed
'\"	to .AP later.  If args are omitted, default tab stops are used.
'\"
'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
'\"	enclosed in one large box.
'\"
'\" .BE
'\"	End of box enclosure.
'\"
'\" .CS
'\"	Begin code excerpt.
'\"
'\" .CE
'\"	End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"	Begin vertical sidebar, for use in marking newly-changed parts
'\"	of man pages.  The first argument is ignored and used for recording
'\"	the version when the .VS was added, so that the sidebars can be
'\"	found and removed when they reach a certain age.  If another argument
'\"	is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"	End of vertical sidebar.
'\"
'\" .DS
'\"	Begin an indented unfilled display.
'\"
'\" .DE
'\"	End of indented unfilled display.
'\"
'\" .SO
'\"	Start of list of standard options for a Tk widget.  The
'\"	options follow on successive lines, in four columns separated
'\"	by tabs.
'\"
'\" .SE
'\"	End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\"	Start of description of a specific option.  cmdName gives the
'\"	option's name as specified in the class command, dbName gives
'\"	the option's name in the option database, and dbClass gives
'\"	the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\"	Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id$
'\"
'\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
'\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1	\\fI\\$2\\fP	(\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1	\\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
'\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"	# BS - start boxed text
'\"	# ^y = starting y location
'\"	# ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
'\"	# BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
'\"	# ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
..
'\"	# VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.ev 2
.nf
.ti 0
.mk ^t
\h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
.sp -1
.fi
.ev
.\}
.nr ^v 0
..
'\"	# Special macro to handle page bottom:  finish off current
'\"	# box/sidebar if in box/sidebar mode, then invoked standard
'\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"	Draw three-sided box if this is the box's first page,
.\"	draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
.bp
'fi
.ev
.if \\n(^b \{\
.mk ^y
.nr ^b 2
.\}
.if \\n(^v \{\
.mk ^Y
.\}
..
'\"	# DS - begin display
.de DS
.RS
.nf
.sp
..
'\"	# DE - end display
.de DE
.fi
.RE
.sp
..
'\"	# SO - start of list of standard options
.de SO
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
'\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR manual entry for details on the standard options.
..
'\"	# OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
..
'\"	# CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
'\"	# CE - end code excerpt
.de CE
.fi
.RE
..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH scan n 8.4 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
scan \- Parse string using conversion specifiers in the style of sscanf
.SH SYNOPSIS
\fBscan \fIstring format \fR?\fIvarName varName ...\fR?
.BE

.SH INTRODUCTION
.PP
This command parses fields from an input string in the same fashion as the
ANSI C \fBsscanf\fR procedure and returns a count of the number of
conversions performed, or -1 if the end of the input string is reached
before any conversions have been performed.  \fIString\fR gives the input
to be parsed and \fIformat\fR indicates how to parse it, using \fB%\fR
conversion specifiers as in \fBsscanf\fR.  Each \fIvarName\fR gives the
name of a variable; when a field is scanned from \fIstring\fR the result is
converted back into a string and assigned to the corresponding variable.
If no \fIvarName\fR variables are specified, then \fBscan\fR works in an
inline manner, returning the data that would otherwise be stored in the
variables as a list.  In the inline case, an empty string is returned when
the end of the input string is reached before any conversions have been
performed.

.SH "DETAILS ON SCANNING"
.PP
\fBScan\fR operates by scanning \fIstring\fR and \fIformat\fR together.
If the next character in \fIformat\fR is a blank or tab then it
matches any number of white space characters in \fIstring\fR (including
zero).
Otherwise, if it isn't a \fB%\fR character then it 
must match the next character of \fIstring\fR.
When a \fB%\fR is encountered in \fIformat\fR, it indicates
the start of a conversion specifier.
.VS 8.4
A conversion specifier contains up to four fields after the \fB%\fR:
a \fB*\fR, which indicates that the converted value is to be discarded 
instead of assigned to a variable; a XPG3 position specifier; a number
indicating a maximum field width; a field size modifier; and a
conversion character.
.VE 8.4
All of these fields are optional except for the conversion character.
The fields that are present must appear in the order given above.
.PP
When \fBscan\fR finds a conversion specifier in \fIformat\fR, it
first skips any white-space characters in \fIstring\fR (unless the
specifier is \fB[\fR or \fBc\fR).
Then it converts the next input characters according to the 
conversion specifier and stores the result in the variable given
by the next argument to \fBscan\fR.
.PP
If the \fB%\fR is followed by a decimal number and a \fB$\fR, as in
``\fB%2$d\fR'', then the variable to use is not taken from the next
sequential argument.  Instead, it is taken from the argument indicated
by the number, where 1 corresponds to the first \fIvarName\fR.  If
there are any positional specifiers in \fIformat\fR then all of the
specifiers must be positional.  Every \fIvarName\fR on the argument
list must correspond to exactly one conversion specifier or an error
is generated, or in the inline case, any position can be specified
at most once and the empty positions will be filled in with empty strings.
.PP
The following conversion characters are supported:
.TP 10
\fBd\fR
The input field must be a decimal integer.
It is read in and the value is stored in the variable as a decimal string.
.VS 8.4
If the \fBl\fR or \fBL\fR field size modifier is given, the scanned
value will have an internal representation that is at least 64-bits in
size.
.VE 8.4
.TP 10
\fBo\fR
The input field must be an octal integer. It is read in and the 
value is stored in the variable as a decimal string.
.VS 8.4
If the \fBl\fR or \fBL\fR field size modifier is given, the scanned
value will have an internal representation that is at least 64-bits in
size.
If the value exceeds MAX_INT (017777777777 on platforms using 32-bit
integers when the \fBl\fR and \fBL\fR modifiers are not given), it
will be truncated to a signed integer.  Hence, 037777777777 will
appear as -1 on a 32-bit machine by default.
.VE 8.4
.TP 10
\fBx\fR
The input field must be a hexadecimal integer. It is read in 
and the value is stored in the variable as a decimal string.
.VS 8.4
If the \fBl\fR or \fBL\fR field size modifier is given, the scanned
value will have an internal representation that is at least 64-bits in
size.
If the value exceeds MAX_INT (0x7FFFFFFF on platforms using 32-bit
integers when the \fBl\fR and \fBL\fR modifiers are not given), it
will be truncated to a signed integer.  Hence, 0xFFFFFFFF will appear
as -1 on a 32-bit machine.
.VE 8.4
.TP 10
\fBu\fR
The input field must be a decimal integer.  The value is stored in the
variable as an unsigned decimal integer string.
.VS 8.4
If the \fBl\fR or \fBL\fR field size modifier is given, the scanned
value will have an internal representation that is at least 64-bits in
size.
.VE 8.4
.TP 10
\fBi\fR 
The input field must be an integer.  The base (i.e. decimal, octal, or
hexadecimal) is determined in the same fashion as described in
\fBexpr\fR.  The value is stored in the variable as a decimal string.
.VS 8.4
If the \fBl\fR or \fBL\fR field size modifier is given, the scanned
value will have an internal representation that is at least 64-bits in
size.
.VE 8.4
.TP 10
\fBc\fR
A single character is read in and its binary value is stored in 
the variable as a decimal string.
Initial white space is not skipped in this case, so the input
field may be a white-space character.
This conversion is different from the ANSI standard in that the
input field always consists of a single character and no field
width may be specified.
.TP 10
\fBs\fR
The input field consists of all the characters up to the next 
white-space character; the characters are copied to the variable.
.TP 10
\fBe\fR or \fBf\fR or \fBg\fR
The input field must be a floating-point number consisting 
of an optional sign, a string of decimal digits possibly
containing a decimal point, and an optional exponent consisting 
of an \fBe\fR or \fBE\fR followed by an optional sign and a string of 
decimal digits.
It is read in and stored in the variable as a floating-point string.
.TP 10
\fB[\fIchars\fB]\fR
The input field consists of any number of characters in 
\fIchars\fR.
The matching string is stored in the variable.
If the first character between the brackets is a \fB]\fR then
it is treated as part of \fIchars\fR rather than the closing
bracket for the set.
If \fIchars\fR
contains a sequence of the form \fIa\fB\-\fIb\fR then any
character between \fIa\fR and \fIb\fR (inclusive) will match.
If the first or last character between the brackets is a \fB\-\fR, then
it is treated as part of \fIchars\fR rather than indicating a range.
.TP 10
\fB[^\fIchars\fB]\fR
The input field consists of any number of characters not in 
\fIchars\fR.
The matching string is stored in the variable.
If the character immediately following the \fB^\fR is a \fB]\fR then it is 
treated as part of the set rather than the closing bracket for 
the set.
If \fIchars\fR
contains a sequence of the form \fIa\fB\-\fIb\fR then any
character between \fIa\fR and \fIb\fR (inclusive) will be excluded
from the set.
If the first or last character between the brackets is a \fB\-\fR, then
it is treated as part of \fIchars\fR rather than indicating a range.
.TP 10
\fBn\fR
No input is consumed from the input string.  Instead, the total number
of characters scanned from the input string so far is stored in the variable.
.LP
The number of characters read from the input for a conversion is the
largest number that makes sense for that particular conversion (e.g.
as many decimal digits as possible for \fB%d\fR, as 
many octal digits as possible for \fB%o\fR, and so on).
The input field for a given conversion terminates either when a
white-space character is encountered or when the maximum field 
width has been reached, whichever comes first.
If a \fB*\fR is present in the conversion specifier 
then no variable is assigned and the next scan argument is not consumed.

.SH "DIFFERENCES FROM ANSI SSCANF"
.PP
The behavior of the \fBscan\fR command is the same as the behavior of
the ANSI C \fBsscanf\fR procedure except for the following differences:
.IP [1]
\fB%p\fR conversion specifier is not currently supported.
.IP [2]
For \fB%c\fR conversions a single character value is
converted to a decimal string, which is then assigned to the
corresponding \fIvarName\fR;
no field width may be specified for this conversion.
.IP [3]
.VS 8.4
The \fBh\fR modifier is always ignored and the \fBl\fR and \fBL\fR
modifiers are ignored when converting real values (i.e. type
\fBdouble\fR is used for the internal representation).
.VE 8.4
.IP [4]
If the end of the input string is reached before any conversions have been
performed and no variables are given, an empty string is returned.

.SH "SEE ALSO"
format(n), sscanf(3)

.SH KEYWORDS
conversion specifier, parse, scan
