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B5015 - Why are my file path names not working! [The dangers of backslashes!]

by - Joseph Ganci

Does anyone know why

varList:=ReadExtFile(RecordsLocation^"infoList.txt")

and

varList:=ReadExtFile("c:\win\A5w_data\infoList.txt")

both return the contents of "infoList.txt". However, if I create my own training_data directory

varList:=ReadExtFile("c:\win\train\infoList.txt")

no value is returned?

AH-HA! Count yourself as the latest victim of the double-backslash beast! This drove my officemate nuts once for quite a while until I pointed out the error of his ways.

Here's what the problem is:

The backslash character is an escape character in Authorware. This means that what follows the backslash is important. If you follow it with an "r" for instance, \r, this means a return character, so that if var was:

var := "Joe\ris great."

showing var on the screen would show:

Joe
is great.

Here's another:

var := "Joe\ris\treally great!"

will get you:

Joe
is         really great!

What!?! The \t counts as a tab character in Authorware.

Now there are a handful of characters that can combine with the backslash to make an escape character, but most don't, and in those cases the backslash is counted as a normal backslash. See where this is headed? That's the case in your line:

varList:=ReadExtFile("c:\win\A5w_data\infoList.txt")

The letters w, a, and i don't combine with a \ to make an escape character, so the line works as is.

BUT (and this is a really big BUT)

The line:

varList:=ReadExtFile("c:\win\train\infoList.txt")

has a letter t after the backslash, making it a Tab character. You can now see it like this:

varList:=ReadExtFile("c:\winTABrain\infoList.txt")

Oops! If you had chosen a directory name that didn't start with a t, r, or n (and a couple of other characters) you would have been fine.

So how do you get a freaking backslash character to stay put? Use a second backslash: \\. This gets interpreted in Authorware as one backslash.

The ultimate solution? In file paths, always use two backslashes where one will normally go:

varList:=ReadExtFile("c:\\win\\train\\infoList.txt")

will be interpreted as:

varList:=ReadExtFile("c:\win\train\infoList.txt")

Oh, and you know those UNC network drives that start with two backlashes normally, like:

\\MyServer\MyFolder\MyFile.txt

Well you would need to write that as:

\\\\MyServer\\MyFolder\\MyFile.txt

Fun, huh?

A quick experiment will bear this out. Try typing in a Calc icon:

var := "c:\myfolder\tmyfile.txt"

Close the Calc, then reopen it. You will now see:

var := "c:\\myfolder\tmyfile.txt"

Notice that Authorware saw that the first backslash could not combine with an m to be an escape character, so it added a second backslash for you for good measure. On the second backslash combination, though, it saw that \t could be a legimimate escape sequence, so it didn't change that one. Tricky, huh?

Tom Adams added:
You might want to mention that what you describe is case-sensitive. AW adds the 2nd backslash IF it sees \T. As you stated, it does not if it sees \t.

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