Rename using RegEx

[Michael Bulgrien]

The rename dialog has an option for renaming using regular expressions, but the help file does not give any examples of a rename using regex. Please provide an example.

In particular, I am hoping that the regex rename overcomes the limitations of a DOS-based rename. In DOS, for example, it is extremely difficult (if not impossible) to rename a group of files by adding or removing a prefix from the front of the filename:

fileone.ext --> new_fileone.ext
filetwo.ext --> new_filetwo.ext
filethree.ext --> new_filethree.ext
filefour.ext --> new_filefour.ext

or

new_fileone.ext --> fileone.ext
new_filetwo.ext --> filetwo.ext
new_filethree.ext --> filethree.ext
new_filefour.ext --> filefour.ext

Likewise, DOS rename cannot change the case of the filenames:

fileone.ext --> FileOne.ext
filetwo.ext --> FileTwo.ext
filethree.ext --> FileThree.ext
filefour.ext --> FileFour.ext

I am hoping that a regex rename will evaluate each file with the regex rules to determine how to rename the file, and that both of these DOS shortcomings can be overcome... but I am not RegEx savvy and would appreciate examples to learn from and model after.

[Chris]

Michael,

To add a prefix, use the following regular expression masks:
Old Mask: (.*)
New Mask: new_$1

Placing () around an expression saves the matched text. To access the saved text, use the variables $1, $2, etc. In regular expressions this is called a "backreference".

I don't know how you would change the character case of a filename using regular expressions.

[Michael Bulgrien]

Great! Removing the prefix was a piece of cake also:

Old Mask: new_(.*)
New Mask: $1

Edit: I've since discovered that a regular expression rename does not have to represent the entire file name. To remove the prefix, all I had to do was specify the prefix in the Old Mask and leave the New Mask blank.

[Michael Bulgrien]

I don't know how you would change the character case of a filename using regular expressions.

According to my quick research, perl should change case with \U if you have the backreference in double quotes.

I tried this:

Old Mask: file(.)(.*)
New Mask: "File\u$1$2"

But Cirrus tells me that "Target filename is invalid".

[Michael Bulgrien]

According to my research:

\l and \u convert the next character to lower or upper case, respectively

\L or \U indicates a lasting conversion of case, until terminated by \E or thrown over by another \U or \L

If there is no \E , case is converted until the end of the string.

The regexps \L\u$word or \u\L$word convert the first character of $word to uppercase and the rest of the characters to lowercase.

[Michael Bulgrien]

Could I have an update on this, please. The help file says "Perl-compatible regular expressions" and the case-conversion syntax above is from the Perl web site. Can BC3 be made to correctly interpret this syntax?

[Tim]

We'll look into this when we have some time, but as our help file says: "The regular expression support in Beyond Compare is a subset of the Perl Compatible Regular Expression (PCRE) syntax."