Re: Program to change a set of file names all at once?
Command prompt would work in some instances, but from the research I've done, I don't think it's as powerful or flexible as PowerShell. Someone feel free to correct me if I'm wrong. I do know that regular expressions don't work in command prompt when renaming files.
The basic gist of the PowerShell command is this:
get-ChildItem | rename-item -newname {$_.name -replace 'insert regular _expression_ here','string to replace any matches with'}
Now I'll break it down piece by piece:
get-ChildItem: lists all the files in a directory, just like cd in command prompt. If you want the command to list and/or operate on the current folder and all subfolders, add the -recurse switch. You can also do something like get-ChildItem *.mp3 if you only want to list files with the .mp3 extension.
| (vertical bar): feeds the output of get-ChildItem to the next command.
rename-item -newname: Takes all the files fed into it from get-ChildItem and changes them depending on the _expression_ that is given to the -newname switch.
{$_.name: The left brace opens up a script block. The $_.name just says "do something to the name of each file that you receive."
-replace: This is a PowerShell operator that allows you to replace part of a file name or list of file names with something else or nothing at all if you so choose.
'insert regular _expression_ here': Regular expressions would take far too long to explain adequately, but there are lots of tutorials that are only a Google search away. I'll give a few examples of what you could do at the end.
'string to replace any matches with': You can put some text here or an empty string, and the part of the file name(s) that match the regular _expression_ will be replaced with whatever you want.
}: closes the script block
Clarifying examples:
get-ChildItem | rename-item -newname {$_.name -replace 'cat','dog'}: replaces all instances of cat with the string 'dog'
get-ChildItem | rename-item -newname {$_.name -replace 'cat',''}: replaces all instances of cat with an empty string, which removes it from each file name
Here's where the power of regular expressions starts to come into play. For these examples, let's say you have an SFX library like an idiot and you want to remove the first part of each file name. You could do something like this:
get-ChildItem | rename-item -newname {$_.name -replace '^.+? - ',''}: Says "only match at the beginning of each file name (^) and match one or more of any character (.+), followed by a space, a dash and another space. Replace any matches you find with an empty string." As for the question mark after the +, that just tells the regex engine to stop as soon as the pattern is matched rather than match as much as it can. This is called greedy vs lazy matching if you want to find out more.
For example, if we have a bunch of sound effects that are explosions, and they have the string "Explosions - " at the beginning of each file name, the regex engine will match on it and replace it with an empty string. We tell the engine to lazy match because if we didn't, the engine would keep going after the string " - ". If we had a file name like "Explosions - Vol. 1 - bomb.wav", the lazy match would stop after "Explosions - ", leaving us with "Vol. 1 - bomb.wav". If we left off the question mark, however, it would match on "Explosions - Vol. 1 - ", just leaving us with bomb.wav. Both types of matching have their uses and it's up to you whether to use one or the other.
I hope this has been helpful. If you have any questions, let me know and I'll try to help you out. There is a lot to learn about regular expressions, and I barely scratched the surface here. I found that the tutorials at https://www.regular-expressions.info/tutorialcnt.html helped me increase my understanding of regular expressions.
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