Rename files, using text-file as source

Question

In a folder, i've 600 files, numbered from 001 to 600. It looks like foo_001.bar. In a text file, i've the number & titles of this folder. Now i want to rename foo_001.bar with the corresponding 001 title foobar from the text file.

But i don't have a clue how to do this properly on Linux Mint. Can someone help me or give me a tip?

Content of the titles.txt looks like this. With a tab (can be altered easy off course) between the number and the title.

001 title of 1
002 this is 2
003 and here goes 3
004 number four
005 hi this is five
etc

Content of the folder looks like this. No exceptions.

file_001.ext
file_002.ext
file_003.ext
file_004.ext
file_005.ext
etc

Answer 1

Just loop through your file with read, get the seperated columns with awk cut (Thank you, @Jack) and mv your file accordingly. In this very simple implementation I assume that your text file containing the new names is located at ./filenames and your script is called from the directory containing your files.

#!/bin/bash
while IFS='' read -r line || [[ -n "$line" ]]; do
        NR=$(echo "$line" | cut -f 1)
        NAME=$(echo "$line" | cut -f 2)
        if [ -f "foo_${NR}.ext" ] ; then
                mv "foo_${NR}.ext" "$NAME"
        fi
done < filenames