I never cease to be amazed at the number of different ways that data can be encoded into simple test lines ... and how the various languages that we teach can be used to manipulate / extract pertinent information. Today, on a Tcl Course, I was presented with data in this form:
  T/N/R/Brother/Sister/Mum/Bob.txt/Esmerelda.txt/Sophie.txt

The first three fields can be disregarded. The rest of the line lists a series of relationships (and unspecified number from 0 up) followed by a series of file names, each of which relates to a relationship. Nothing nice like them being in pairs on the line - it's all the relationships followed by all the file names.

Solution?
 1. Reformat the line into a list with split
 2. Calculate the number of relationships with expr
 3. Loop (a for loop) through each relationship
 4. In the loop, calculate positions of the relationship and file name with expr
 5. Extract the field you want with lindex
Complete source code example [here]
(written 2011-05-10)

 T206 - Tcl/Tk - Lists
  [3618] lists and struct::list in Tcl - Introduction to struct::list and examples - (2012-02-18)
  [3583] Expanding a list of parameters in Tcl - {*} and eval - (2012-01-17)
  [3582] Tcl collections - lists, dicts and array - (2012-01-16)
  [3415] User defined sorting and other uses of callbacks in Tcl and Tk - (2011-09-02)
  [3394] The difference between lists and strings - Tcl - (2011-08-16)
  [2472] split and join in tcl and expect - (2009-10-23)
  [2468] What are Tcl lists? - (2009-10-22)
  [1601] Replacing the last comma with an and - (2008-04-04)
  [1405] Sorting in Tcl - lists and arrays - (2007-10-24)
  [1402] Tcl - append v lappend v concat - (2007-10-23)
  [1334] Stable sorting - Tcl, Perl and others - (2007-09-06)
  [1283] Generating traffic for network testing - (2007-07-29)
  [1282] Stringing together Tcl scripts - (2007-07-29)
  [781] Tcl - lappend v concat - (2006-06-27)
  [463] Splitting the difference - (2005-10-13)
  [144] Tcl sandwich - lists in Tcl - (2004-12-08)

T205 - Tcl/Tk - String Handling in Tcl
  [3576] Tcl - apparently odd behaviour of string trimleft - (2012-01-13)
  [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04)
  [1410] Tcl / regsub - changing a string and using interesting bits - (2007-10-27)
  [1403] Square Bracket protection in Tcl - (2007-10-23)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [779] The fragility of pancakes - and better structures - (2006-06-26)
  [404] How to check that a string contains a number in Tcl - (2005-08-06)

Back to What to do in the evening during a Tcl course

Previous and next or Horse's mouth home

Forward to Should we cover expect and/or Tk on our public Tcl courses?

New Camera - very first picture, and next from first films
Random Questions ...
Exceptions - Tcl style
Should we cover expect and/or Tk on our public Tcl courses?
Extracting data from a string / line from file - Tcl
What to do in the evening during a Tcl course
The juggler
The future of canal management and charities - Kennet and Avon Canal bias
Does Well House Manor Hotel in Melksham offer lots of discounts?
Passing parameters to Python functions - the options you have