scan (n)

SYNOPSIS

scan string format varName ?varName ...?

INTRODUCTION

This command parses fields from an input string in the same fashion as the ANSI C sscanf 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. String gives the input to be parsed and format indicates how to parse it, using % conversion specifiers as in sscanf. Each varName gives the name of a variable; when a field is scanned from string the result is converted back into a string and assigned to the corresponding variable.

DETAILS ON SCANNING

Scan operates by scanning string and formatString together. If the next character in formatString is a blank or tab then it matches any number of white space characters in string (including zero). Otherwise, if it isn't a % character then it must match the next character of string. When a % is encountered in formatString, it indicates the start of a conversion specifier. A conversion specifier contains three fields after the %: a *, which indicates that the converted value is to be discarded instead of assigned to a variable; a number indicating a maximum field width; and a conversion character. All of these fields are optional except for the conversion character.

When scan finds a conversion specifier in formatString, it first skips any white-space characters in string. 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 scan. The following conversion characters are supported:

d

The input field must be a decimal integer. It is read in and the value is stored in the variable as a decimal string.

o

The input field must be an octal integer. It is read in and the value is stored in the variable as a decimal string.

x

The input field must be a hexadecimal integer. It is read in and the value is stored in the variable as a decimal string.

c

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.

s

The input field consists of all the characters up to the next white-space character; the characters are copied to the variable.

e or f or g

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 e or E 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.

[chars]

The input field consists of any number of characters in chars. The matching string is stored in the variable. If the first character between the brackets is a ] then it is treated as part of chars rather than the closing bracket for the set.

[^chars]

The input field consists of any number of characters not in chars. The matching string is stored in the variable. If the character immediately following the ^ is a ] then it is treated as part of the set rather than the closing bracket for the set.

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 %d, as many octal digits as possible for %o, 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 * is present in the conversion specifier then no variable is assigned and the next scan argument is not consumed.

DIFFERENCES FROM ANSI SSCANF

The behavior of the scan command is the same as the behavior of the ANSI C sscanf procedure except for the following differences:

%p and %n conversion specifiers are not currently supported.

For %c conversions a single character value is converted to a decimal string, which is then assigned to the corresponding varName; no field width may be specified for this conversion.

The l, h, and L modifiers are ignored; integer values are always converted as if there were no modifier present and real values are always converted as if the l modifier were present (i.e. type double is used for the internal representation).

KEYWORDS

conversion specifier, parse, scan '\" '\" Copyright (c) 1990-1994 The Regents of the University of California. '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" RCS: @(#) $Id: scrollbar.n,v 1.2 1998/09/14 18:22:59 stanton 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: man.macros,v 1.2 1998/09/14 18:39:54 stanton Exp $ '\" '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. t .wh -1.3i ^B ^l \n(.l b '\" # Start an argument description AP !"\\$4"" .TP \\$4 \{\ !"\\$2"" .TP \\n()Cu .TP 15