'\" '\" 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: @(#) scan.n,v 1.5 2003/01/21 19:40:00 hunt Exp '\" .so man.macros .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