Question

I have a smaller SSIS packat that I am trying to match a file name with VB Regex and delete “said” file. My regex looks like this, ^RegZStmntAdj.[A-z0-9_].\.txt$, and I am trying to figure out why it won’t match any of the files in the directory. This is valid syntax if I am thinking correctly.

RegZStmntAdj2_07272011.txt
RegZStmntAdj1_07272011.txt
RegZStmntAdj2_07272011.txxt
New Text Document.txt

If I run the regex with ^RegZStmntAdj.*.\.txt$, it matches the correct files and deletes them. I know * works, but I would like to learn to make more precise Regular Expressions.

RegZStmntAdj2_07272011.txt
RegZStmntAdj1_07272011.txt

Answer 1

Try the following Regex:

^RegZStmntAdj.[\w_]{9}\.txt$

I’ve used \w, which is the same as A-Za-z0-9, and told it to match 9 characters so that it will match the _<date> part of your filename. You were only matching the first character from there (i.e. the underscore).

Using Powershell to verify:

PS> $test = "^RegZStmntAdj.[\w_]{9}\.txt$"
PS> "RegZStmntAdj2_07272011.txt" -match $test
    True
PS> "RegZStmntAdj1_07272011.txt" -match $test
    True
PS> "RegZStmntAdj2_07272011.txxt" -match $test
    False  # (Correct as contains 2 "xx"s in extension)
PS> "New Text Document.txt" -match $test
    False  # (Correct as nowhere near a match!!)

To make your regex even more precise, you could use ^RegZStmntAdj\d_[\d]{8}\.txt$, which translates to:

A string starting with “RegZStmntAdj”, then a digit, then an
underscore, then 8 digits, then ending in “.txt”

which I believe is what you are looking for.