Rename multiple file in linux

If a directory contains so many files with the extension .txt and if you want to rename it to some other extensions follow the step

# cd /directory/contains/file

shows result before renaming

# rename -n 's/\.txt$/\.bak/' *.txt (file we want to change)

# rename  's/\.txt$/\.html/' *.txt

# rename 's/.txt/.md/i' *

It is useful if the directory contains a lot of files to edit in a single step.

-n, --no-act
 No Action: show what files would have been renamed

* Also we can convert upper case letters to lowercase and  vice versa

# cd /directory/contains/file

# rename 'y/A-Z/a-z/' *

* Renaming file name from:

ctechz.txt0
ctechz.txt1
ctechz.txt2
ctechz.txt3
ctechz.txt4
ctechz.txt5

To file name:

ctechzblog.txt
ctechzblog.txt0
ctechzblog.txt1
ctechzblog.txt2

# rename 's/ctechz/ctechzblog/g' ctechz.txt*