If you have a series of Tcl scripts that you want to run in a sequence, you can
call all of them up in a master script using a series of source commands. This command switches input from the current script (sources) to the new source given as if the text of the sourced file was copied in to the original file from which the source was run at that same point.

Can it be that easy? Not quite - you may have to deal with debris left from previous commands. Although Tcl will not (in most circumstances) let you use a variable that does not exist, there are a few exceptions and if these exceptions are used by the sourced file, you could be in trouble by not starting from a clean sheet. Some of the commands you need to watch are:

append This command will create a new variable if it does not exist, but alter an existing variable if it does exist. If your sourced file uses an append on a variable that is assumed to be initially empty, then a series of calls to that file can cause a buildup of data which you do not want to happen.

lappend This command will create a new variable if it does not exist, but alter an existing variable if it does exist. If your sourced file uses a lappend on a variable that is assumed to be initially emppy, then a series of calls to that file can cause a buildup of data which you do not want to happen.

info exists If you check whether a variable exists as a part of your script to see whether it's just started, bear in mind that with a series of sourced files, it may actually exist from something you've previously pulled in.

array names If you have an array set up in one sourced file and then use that same array in a second sourced file, assuming it to start empty, then commands such as array names will reveal the old information to the new sourced file.

open You should close files once you open them. I know that files do get closed at the end of a script run, but if you source a series of files you can end up with a build-up of open files. This can be a particular issue if one sources file writes to a file, then the next opens it to read it back. Run as two separate Tcl commands, it will all work fine as the file is flushed and closed, but with two files of Tcl sourced from within a single script, it's another matter.
(written 2007-07-29 11:10:04)

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Generating traffic for network testing
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West Wilts - no longer Wet Wilts - show
The Gdansk fireball
West Wilts Show
AgtInvoke - a command to drive Agilent Tcl software extensions
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