# mmv > Move and rename files in bulk. - Rename all files with a certain extension to a different extension: `mmv "*{{.old_extension}}" "#1{{.new_extension}}"` - Copy report6part4.txt to ./french/rapport6partie4.txt along with all similarly named files: `mmv -c {{"report*part*.txt"}} {{"./french/rapport#1partie#2.txt"}}` - Append all .txt files into one file: `mmv -a {{"*.txt"}} {{"all.txt"}}` - Convert dates in filenames from "M-D-Y" format to "D-M-Y" format: `mmv {{"[0-1][0-9]-[0-3][0-9]-[0-9][0-9][0-9][0-9].txt"}} {{"#3#4-#1#2-#5#6#7#8.txt"}}`