[kwlug-disc] bash - file renaming

[Chris Irwin]

On Thu, Sep 26, 2019, at 08:02, Cedric Puddy wrote:
> I've always done as Jason suggests, but the one thing that is usually helpful is the addition of "basename":
> 
>> for $FILE in *
>> do
>> mv $FILE $(basename $FILE .htm).whatever
>> done
> 
> Basename will remove an arbitrary string (eg: .htm) from the end of another string, thus getting rid of the old extension, so you can tack on your new ".html" or ".whatever" extension.

For a one-off, this is generally what I do too.

However, if you're scripting a loop, it may save a fair amount of time by switching to bash builtins instead of calling basename in every loop. I recently cut down a script that took ~12 seconds to run to about 1 second by eliminating sed and basename calls from within a loop. (the output fed a user screen, so it was noticeable). Also, it stopped churning through a few thousand PIDs while running.

(Also, don't forget quotes, or you'll have a bad time)

for FILE in *
 do
 # Echo just for safety incase somebody copy/pastes this.
 echo mv "$FILE" "${FILE%.*}.whatever"
 done

-- 
*Chris Irwin*

email: chris at chrisirwin.ca
 xmpp: chris at chrisirwin.ca
 web: https://chrisirwin.ca
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