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Top Forums Shell Programming and Scripting Help me to understand some regular expresions usage Post 302173482 by alex_5161 on Thursday 6th of March 2008 07:41:17 PM
Old 03-06-2008
Help me to understand some regular expresions usage

Can someone explain me how those restatements are constructed
Code:
        suffix=${name#*.}
        prefix=${main%%+([0-9])}
        num=10#${num}

1. What is the logic to use a reg-expr in variable name
2. In first string - the '#' seems to mean 'everithing after next mached', but the '.' in reg-exp is a one character, here it seems it used litteraly. Why?
3. I guess '%%' means return part that match next expression? Is it correct?
4. Why the '()' used in second string? [0-9] - any digit; '+' one or more times; so, +[0-9] should return consecutive numbers from string?! What is the need in '()'
5. How to understand third line? What is done by that whith string of digits?

Thank you

Last edited by alex_5161; 03-06-2008 at 08:42 PM.. Reason: formatting
 

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textutil::tabify(n)				    Text and string utilities, macro processing 			       textutil::tabify(n)

__________________________________________________________________________________________________________________________________________________

NAME
textutil::tabify - Procedures to (un)tabify strings SYNOPSIS
package require Tcl 8.2 package require textutil::tabify ?0.7? ::textutil::tabify::tabify string ?num? ::textutil::tabify::tabify2 string ?num? ::textutil::tabify::untabify string ?num? ::textutil::tabify::untabify2 string ?num? _________________________________________________________________ DESCRIPTION
The package textutil::tabify provides commands that convert between tabulation and ordinary whitespace in strings. The complete set of procedures is described below. ::textutil::tabify::tabify string ?num? Tabify the string by replacing any substring of num space chars by a tabulation and return the result as a new string. num defaults to 8. ::textutil::tabify::tabify2 string ?num? Similar to ::textutil::tabify this command tabifies the string and returns the result as a new string. A different algorithm is used however. Instead of replacing any substring of num spaces this command works more like an editor. num defaults to 8. Each line of the text in string is treated as if there are tabstops every num columns. Only sequences of space characters containing more than one space character and found immediately before a tabstop are replaced with tabs. ::textutil::tabify::untabify string ?num? Untabify the string by replacing any tabulation char by a substring of num space chars and return the result as a new string. num defaults to 8. ::textutil::tabify::untabify2 string ?num? Untabify the string by replacing any tabulation char by a substring of at most num space chars and return the result as a new string. Unlike textutil::tabify::untabify each tab is not replaced by a fixed number of space characters. The command overlays each line in the string with tabstops every num columns instead and replaces tabs with just enough space characters to reach the next tabstop. This is the complement of the actions taken by ::textutil::tabify::tabify2. num defaults to 8. There is one asymmetry though: A tab can be replaced with a single space, but not the other way around. BUGS, IDEAS, FEEDBACK This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category textutil of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation. SEE ALSO
regexp(n), split(n), string(n) KEYWORDS
formatting, string, tabstops CATEGORY
Text processing textutil 0.7 textutil::tabify(n)
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