Strip Characters Before Period If Filename Has Prefix in Bash

Question

I have a directory that looks like this:

pages/
 folder1/
  folder1.filename1.txt
  folder1.filename2.txt
 folder2/
  folder2.filename4.txt
  folder2.filename5.txt
 folder3/
  filename6.txt

I want it to look like this:

pages/
 folder1/
  filename1.txt
  filename2.txt
 folder2/
  filename3.txt
  filename4.txt
 folder3/
  filename5.txt

With ls * | sed -e s/^[^.]*.// > /tmp/filenames.txt I get a file containing:

filename1.txt
filename2.txt
filename3.txt
filename4.txt
txt

How can I tell sed to ignore filenames of the form [filename].[suffix] and only look at filenames of the form [foldername].[filename].[suffix]?

The final script (as pointed out, the find command would simplify things, but this worked):

for folder in $(ls .)
do
    if test -d $folder
    then
     pushd $folder
       ls * | sed 's/.*\.\(.*\..*\)/\1/' > /tmp/filenames.txt
       ls * > /tmp/current.txt

       exec 3</tmp/current.txt
       exec 4</tmp/filenames.txt

       while read file <&3; read name <&4;
       do
        mv "$file" "$name"
       done

       rm /tmp/current.txt
       rm /tmp/filenames.txt
     popd
    else
     echo $folder "not a directory"
    fi
done

exit 0

This page is now a community wiki. You can add more elegant solutions below:

for folder in $(ls .)
do 
     something better

Answer 1

use the following regex:

/\A(.\*?\\.){2,2}.+\Z/

Answer 2

Give this a try:

sed 's/.*\.\(.*\..*\)/\1/'

You should really use find then you wouldn't need the check for "-d folder" or the temp file and execs or the while loop.

You can avoid the temporary file by using process substition:

while read line
do
    echo $line
done < <(ls)

Another item of interest: your system may already have a Perl script called rename or prename which will rename files using a regular expression.

Answer 3

You don't need to use sed:

ls * > /tmp/current.txt
exec 3</tmp/current.txt
while read file <&3;
do
    replacement=${file#${folder}.}
    if [ "$replacement" != "txt" ] ; then
        mv "$file" "$replacement"
    fi
done