Need help understanding this script.

Shell Programming and Scripting
1

Can someone explain what is happening line by line in this script, particularly after the do statement. The script works, it renames all the files in my directory that has a date in the file name. But I would like to know more about it.

#!/bin/bash
newdate=12-10-1995
for file in *[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]*
do
mv $file ${file%[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9].*}$newdate${file#*[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]}
done

2

It tries to rename any file with 2-2-4 digit date in the name and replace that date with a new date, but it contains an error as the dot should not be there.
It use parameter expansion to accomplish this.

newdate=12-10-1995
for file in *[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]*
do
  mv "$file" "${file%[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]*}$newdate${file#*[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]}"
done

And it is better to put double quotes there.

3

what does $file " "${file% -- do and $newdate${file#* -- whats this.

4

It cuts of part of the string, see the link.

5

Ok, thanks again.

6

Unless the target filename has a real dot there.

7

Good point :b: