141 lines
5.4 KiB
Plaintext
141 lines
5.4 KiB
Plaintext
'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) scan.n 1.11 96/03/25 20:22:44
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'\"
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.so man.macros
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.TH scan n "" Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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scan \- Parse string using conversion specifiers in the style of sscanf
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.SH SYNOPSIS
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\fBscan \fIstring format varName \fR?\fIvarName ...\fR?
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.BE
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.SH INTRODUCTION
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.PP
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This command parses fields from an input string in the same fashion
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as the ANSI C \fBsscanf\fR procedure and returns a count of the number
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.VS
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of conversions performed, or -1 if the end of the input string is
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reached before any conversions have been performed.
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.VE
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\fIString\fR gives the input to be parsed and \fIformat\fR indicates
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how to parse it, using \fB%\fR conversion specifiers as in \fBsscanf\fR.
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Each \fIvarName\fR gives the name of a variable; when a field is
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scanned from \fIstring\fR the result is converted back into a string
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and assigned to the corresponding variable.
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.SH "DETAILS ON SCANNING"
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.PP
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\fBScan\fR operates by scanning \fIstring\fR and \fIformatString\fR together.
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If the next character in \fIformatString\fR is a blank or tab then it
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matches any number of white space characters in \fIstring\fR (including
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zero).
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Otherwise, if it isn't a \fB%\fR character then it
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must match the next character of \fIstring\fR.
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When a \fB%\fR is encountered in \fIformatString\fR, it indicates
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the start of a conversion specifier.
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A conversion specifier contains three fields after the \fB%\fR:
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a \fB*\fR, which indicates that the converted value is to be discarded
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instead of assigned to a variable; a number indicating a maximum field
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width; and a conversion character.
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All of these fields are optional except for the conversion character.
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.PP
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When \fBscan\fR finds a conversion specifier in \fIformatString\fR, it
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first skips any white-space characters in \fIstring\fR.
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Then it converts the next input characters according to the
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conversion specifier and stores the result in the variable given
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by the next argument to \fBscan\fR.
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The following conversion characters are supported:
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.TP 10
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\fBd\fR
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The input field must be a decimal integer.
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It is read in and the value is stored in the variable as a decimal string.
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.TP 10
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\fBo\fR
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The input field must be an octal integer. It is read in and the
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value is stored in the variable as a decimal string.
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.TP 10
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\fBx\fR
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The input field must be a hexadecimal integer. It is read in
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and the value is stored in the variable as a decimal string.
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.TP 10
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\fBc\fR
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A single character is read in and its binary value is stored in
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the variable as a decimal string.
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Initial white space is not skipped in this case, so the input
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field may be a white-space character.
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This conversion is different from the ANSI standard in that the
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input field always consists of a single character and no field
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width may be specified.
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.TP 10
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\fBs\fR
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The input field consists of all the characters up to the next
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white-space character; the characters are copied to the variable.
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.TP 10
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\fBe\fR or \fBf\fR or \fBg\fR
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The input field must be a floating-point number consisting
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of an optional sign, a string of decimal digits possibly
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containing a decimal point, and an optional exponent consisting
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of an \fBe\fR or \fBE\fR followed by an optional sign and a string of
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decimal digits.
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It is read in and stored in the variable as a floating-point string.
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.TP 10
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\fB[\fIchars\fB]\fR
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The input field consists of any number of characters in
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\fIchars\fR.
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The matching string is stored in the variable.
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If the first character between the brackets is a \fB]\fR then
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it is treated as part of \fIchars\fR rather than the closing
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bracket for the set.
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.TP 10
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\fB[^\fIchars\fB]\fR
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The input field consists of any number of characters not in
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\fIchars\fR.
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The matching string is stored in the variable.
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If the character immediately following the \fB^\fR is a \fB]\fR then it is
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treated as part of the set rather than the closing bracket for
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the set.
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.LP
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The number of characters read from the input for a conversion is the
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largest number that makes sense for that particular conversion (e.g.
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as many decimal digits as possible for \fB%d\fR, as
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many octal digits as possible for \fB%o\fR, and so on).
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The input field for a given conversion terminates either when a
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white-space character is encountered or when the maximum field
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width has been reached, whichever comes first.
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If a \fB*\fR is present in the conversion specifier
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then no variable is assigned and the next scan argument is not consumed.
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.SH "DIFFERENCES FROM ANSI SSCANF"
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.PP
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The behavior of the \fBscan\fR command is the same as the behavior of
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the ANSI C \fBsscanf\fR procedure except for the following differences:
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.IP [1]
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.VS
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\fB%p\fR and \fB%n\fR conversion specifiers are not currently
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supported.
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.VE
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.IP [2]
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For \fB%c\fR conversions a single character value is
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converted to a decimal string, which is then assigned to the
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corresponding \fIvarName\fR;
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no field width may be specified for this conversion.
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.IP [3]
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.VS
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The \fBl\fR, \fBh\fR, and \fBL\fR modifiers are ignored; integer
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values are always converted as if there were no modifier present
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and real values are always converted as if the \fBl\fR modifier
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were present (i.e. type \fBdouble\fR is used for the internal
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representation).
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.VE
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.SH KEYWORDS
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conversion specifier, parse, scan
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