How to add formatting to, and batch rename filenames?

Question

I have around 7,000 .txt files that have been spat out by a program where the naming convention clearly broke. The only saving grace is that they follow the following structure: id, date, time.

m031060209104704.txt --> id:m031 date:060209 time:104704.txt

Sample of other filenames (again same thing):

115-060202105710.txt --> id:115- date:060202 time: 105710.txt

x138051203125338.txt etc...

9756060201194530.txt etc..

I want to rename all 7,000 files in this directory to look like the following:

m031060209104704.txt --> 090206_104704_m031.txt

i.e date_time_id (each separated by underscores or hyphens, I don't mind). I need the date format to be switched from yymmdd to ddmmyy as shown directly above though!

I'm not clear on whats overkill here, full program script or bash command (MAC OS). Again, I don't mind, any and all help is appreciated.

Answer 1

Try something like:

#!/bin/bash

# directory to store renamed files
newdir="./renamed"
mkdir -p $newdir

for file in *.txt; do
    if [[ $file =~ ^(....)([0-9]{2})([0-9]{2})([0-9]{2})([0-9]{6})\.txt$ ]]; then
        # extract parameters
        id=${BASH_REMATCH[1]}
        yy=${BASH_REMATCH[2]}
        mm=${BASH_REMATCH[3]}
        dd=${BASH_REMATCH[4]}
        time=${BASH_REMATCH[5]}

        # then rearrange them to new name
        newname=${dd}${mm}${yy}_${time}_${id}.txt

        # move to new directory
        mv "$file" "$newdir/$newname"
    fi
done