Tcl is an excellent language for combing through and reformatting data - though rarely a first choice language for such tasks if users aren't doing other things with it too.

Towards the end of last week's Learning to program in TCL course, a "side task" requirement came up to reformat our course diary into a .csv file so that a reseller who sells our courses to fill gaps / niches in his own more generic schedule.

Data of the form
  30,11,2015 EL 8
needs to be transformed into data of the form
  ELFULL,30/11/2015,09:00,04/12/2015,17:00,Standard,1,1,SN12 7NY,En-GB,1350,1350,GBP,Well House,Learning to Program in Perl,Other (IT)Code

Complete program [here] and sample data [here].

The main code is as simple as
  loadDataWH "diary" intoHere
  saveDataQA "qa.csv" intoHere
so you can see that even in Tcl, we're using good, structured programming techniques - in this case letting me provide a number of different input formats and a number of output genereators.

Other points of note ...

• calculating end date from start date, allowing for month and year ends:

  set starts [clock scan "$day,$month,$year 12 00" -format "%d,%m,%Y %H %M"]
  set ends [expr $starts + ($courselength -1) * 3600 * 24]
  set eday [clock format $ends -format %e]
  set emonth [clock format $ends -format %m]
  set eyear [clock format $ends -format %Y]

reduces day, month, year of start to seconds from 1.1.1970, adds the number of days of the course (*3600*24) to make it seconds, and converts back. Much easier than trying to work out month lengths, especially for February in leap years.

• course names ending in "P" are 4 days and "L" are five days:

  set courselength 5
  set courseformat {Learning to Program in %s}
  if {[regexp {P$} $coursecode]} {
    set courselength 4
    set courseformat {%s Programming}
  }

• use of upvar to pass big chunks of data out of and into procs effectively and easily.

• allowing blank lines on input to be ignored

  if {[string length $lyne] < 1} continue

• ... and many other useful techniques, worth a study!

(written 2015-10-10)

 T209 - Tcl/Tk - File and Directory Handling
  [779] The fragility of pancakes - and better structures - (2006-06-26)
  [785] Running external processes in Tcl and Tcl/Tk - (2006-06-29)
  [1407] Reading from another process in Tcl (pipes and sockets) - (2007-10-26)
  [1426] Buffering up in Tcl - the empty coke can comparison - (2007-11-10)
  [1467] stdout v stderr (Tcl, Perl, Shell) - (2007-12-10)
  [2467] Tcl - catching an error before your program crashes - (2009-10-22)
  [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04)
  [3320] Reading the nth line from a file (Perl and Tcl examples) - (2011-06-09)
  [3429] Searching through all the files in or below a directory - Ruby, Tcl, Perl - (2011-09-09)
  [3617] The fileutil package and a list of file system commands in Tcl - (2012-02-18)
  [4461] Reading from a URL, and reading Json, from your Tcl script - (2015-03-12)
  [4523] Catching failed commands and not crashing the program in Tcl - (2015-10-10)

Back to Catching failed commands and not crashing the program in Tcl

Previous and next or Horse's mouth home

Forward to What does Tcl do if you try to run a command that is not defined?

Routing in Flask
Hello Flask world / Python web micro framework
Day trip to Lancaster
What does Tcl do if you try to run a command that is not defined?
Tcl - a new example for data reformatting
Loading packages in your Tcl program
Should we get an AA or Visit Wiltshire hotel assessment?
No cold sales calls please - but delighted to hear from others!
Course Schedule - October 2015 to June 2016