For 2023 (and 2024 ...) - we are now fully retired from IT training. We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!
I am also active in many other area and still look after a lot of web sites - you can find an index ((here)) |
Regular Expression Substitution - Tcl
regexp matches regular expressions in TCL, and it will return the latest match into a series of variables if you specify their names. regsub matches and replaces... not quite such a common requirement, and perhaps something I haven't blogged about in the past.
set newstory [regsub blue $original grey]
Take the string from $original, replace the first occurrence of blue with grey and return the resulting string - which I have saved into a variable called new story
I can replace all occurrences of blue using the -all option:
set newstory [regsub -all blue $original grey]
and I can use part of the incoming search as part of the outgoing string too. In this example:
set newstory [regsub -all {bl(\S+)} $original br\\1]
I have taken all words with "bl" in them and replaces the bl and the rest of the word with br and the rest of the word as it was incoming. Note the capture using round brackets, and the back reference on output to \\1 for the first captured set of brackets. This example changes:
It was a clear blue day and he blew into her blue eyes
into
It was a clear brue day and he brew into her brue eyes
Full example in source code [here]
As taught on last week's Learning to program in Tcl course. This is a public course which runs every few months; the recent one was the final run for 2013, but you can find future dates for 2014 and beyond [here] on our web site.
(written 2013-11-12, updated 2013-11-16)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles T205 - Tcl/Tk - String Handling in Tcl [404] How to check that a string contains a number in Tcl - (2005-08-06) [779] The fragility of pancakes - and better structures - (2006-06-26) [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25) [1403] Square Bracket protection in Tcl - (2007-10-23) [1410] Tcl / regsub - changing a string and using interesting bits - (2007-10-27) [1601] Replacing the last comma with an and - (2008-04-04) [2472] split and join in tcl and expect - (2009-10-23) [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04) [3285] Extracting data from a string / line from file - Tcl - (2011-05-10) [3576] Tcl - apparently odd behaviour of string trimleft - (2012-01-13) [4454] Everything is a string - even a list - (2015-03-11) [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11) T247 - Tcl/Tk - Advanced Regular Expressions [1195] Regular Express Primer - (2007-05-20) [1305] Regular expressions made easy - building from components - (2007-08-16) [1336] Ignore case in Regular Expression - (2007-09-08) [1412] Sparse and Greedy matching - Tcl 8.4 - (2007-10-27) [1613] Regular expression for 6 digits OR 25 digits - (2008-04-16)
Some other Articles
Lists in Tcl - fundamentals in a commented source code exampleTcl + Tk (Wish) - an introduction and revision exampleException handling in TclWriting the perfect program in Tcl?Regular Expression Substitution - TclWith the Shpigs and DonkeysA weekend away - Four in a Bed returns to Happy Donkey HillExcellent Railfuture conference, but some setup lessonsLooking to the future at Melksham StationEndorsed Perl, Python and PHP training - Tcl, Lua, Ruby and C too!
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This is a page archived from The Horse's Mouth at
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