From Augix' Wiki

Contents 1 Description 2 Principle 3 with the help of * 3.1 Change extension of a lot files 3.2 Change the first underline to dot 3.3 Change the last underline to dot 3.4 Change file name from upper to lower case

Description

When you want change file names in the Unix Shell, you can use # and % to match a part of the file name and replace this part with other strings you want.

Principle

# does the match from the left part of our string variable, and it simply remove the matched part. (minimum matching)

## does the match from the left part of our string variable, and it simply remove the matched part. (maximum matching)

% does the match from the right part of our string variable, and it simply remove the matched part. (minimum matching)

%% does the match from the right part of our string variable, and it simply remove the matched part. (maximum matching)

old="human.fa"
new=chimp${old#human}
echo $old $new

the result is

human.fa chimp.fa

old="music.mp3"
new=${old%mp3}wav
echo $old $new

the result is

music.mp3 music.wav

with the help of *

You can also use the * to help # and % match variable things. Let's see some examples:

Change extension of a lot files

for i in *.wav; do echo $i ${i%.*}.mp3; done

the result is:

a.wav a.mp3
b.wav b.mp3
c.wav c.mp3

for i in *.wav; do mv "$i" "${i%%.wav}.mp3"; done

Change the first underline to dot

for i in *_*; do echo $i ${i%%_*}.${i#*_}; done

result:

ha1_r1_fa ha1.r1_fa
ha1_r2_fa ha1.r2_fa
ha2_r1_fa ha2.r1_fa
ha2_r2_fa ha2.r2_fa

Change the last underline to dot

for i in *_*; do echo $i ${i%_*}.${i##*_}; done

result:

ha1_r1_fa ha1_r1.fa
ha1_r2_fa ha1_r2.fa
ha2_r1_fa ha2_r1.fa
ha2_r2_fa ha2_r2.fa

Change file name from upper to lower case

for i in *; do echo $i `echo $i | tr [:upper:] [:lower:]`; done