Reading the error message carefully can help you see how the computer misinterpreted what you typed

Raymond Chen

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


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