Handy Linux Commands

Recursively Remove All Files With a Specific Extension:

Suppose you want to delete, recursively, all files with a specific file extension (e.g. a Java folder containing .class files). Run the following command:

$ find folderToStart/ -name \*.extension -exec rm {} \;

Bulk Renaming All Files Within a Folder

To replace a string within all files within a folder, just run the following:

$ for i in *; do newname=`echo $i|sed 's/search_txt/replace_txt/g'`; echo $newname; mv $i $newname; done

For more handy applications to bulk renaming using regular expressions, see this.

Check Folder Sizes on System

Very handy tutorial on how to do all aspects of disk space usage, can be found here.