The details have been changed since they aren’t important but the lesson is the same.

A customer had the following problem with a command-line tool:

I’ve created a taglist but I can’t seem to get it to work with the track command. When I ask it to track the taglist, it can’t find it. But if I ask for all my taglists, there it is.

C:\> show taglists
You have 2 taglists:
 active (8 tags)
 closed (6 tags)
C:\> track active
No such tag "active".

Yes, the track command isn’t working, but let’s take a closer look at that error message. It says no such tag. Strange, because you are trying to track a taglist, not a tag. Shouldn’t the error message be no such taglist?

Aha, the problem is that the track command takes a list of tags on the command line, not a taglist name. The error message is correct: There is no such tag called active. Because active isn’t a tag name; it’s a taglist name.

C:\> track -taglist active
Taglist "active" is now being tracked.

Today’s lesson: Look carefully at what the error message complaining about; it may not be what you expect.

Exercise: Diagnose the following error message, given no information about the program being used beyond what is presented here:

I accidentally made a change (transaction number 12345) to the file XYZ, and I want to back it out. But when I run the backout command, I get an error. Can somebody help me?

C:\> backout 12345
12345 - file not found