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Catching failed commands and not crashing the program in Tcl

Archive - Originally posted on "The Horse's Mouth" - 2015-10-10 05:07:47 - Graham Ellis

Where a command may fail in Tcl (causing Tcl to crash), you can defer it within a catch command. That will return a true value if it fails, and an optional extra parameter gives you the associated error message.

A program to look for the biggest file in or below a directory [here] fails if you run it on a tree with any empty folders, at

  set files [glob "$current/*"]

but that problem may be overcome with a catch:

  if {[catch {set files [glob "$current/*"]}]} {
    set $files ""
  }

Updated code [here].

There's a second catch withn our example too - where the code checks for the file size, it's necessary to catch the file size if it might be used on a "special" such as a socket, pipe or device file.

From our Tcl Programming course as run last week.