Change extension of file using shell script

Question

How to change extension of all *.dat files in a directory to *.txt. Shell script should take the directory name as an argument. Can take multiple directories as arguments. Print the log of command result in appending mode with date and timestamp.

Answer 1

Bash can do all of the heavy lifting such as extracting the extension and tagging on a new one. For example:

for file in $1/*.dat ; do mv "$file" "${file%.*}.txt" ; done

Answer 2

Batch File Rename By File Extension in Unix

# change .htm files to .html
for file in *.htm ; do mv $file `echo $file | sed 's/\(.*\.\)htm/\1html/'` ; done

# change .html files to .htm
for file in *.html ; do mv $file `echo $file | sed 's/\(.*\.\)html/\1htm/'` ; done

#change .html files to .shtml
for file in *.html ; do mv $file `echo $file | sed 's/\(.*\.\)html/\1shtml/'` ; done

#change .html files to php
for file in *.html ; do mv $file `echo $file | sed 's/\(.*\.\)html/\1php/'` ; done

so ==>

# change .dat files to .txt
for file in *.dat ; do mv $file `echo $file | sed 's/\(.*\.\)dat /\1txt/'` ; done