[SOLVED] Bash: How to replace 1 with 01 in filename without using rename function

Issue

I have a a set of file wat follow the form L2_error_with_G_at_#_#.csv where the # symbol could be any number between 1 and 16. I want to rename the files using bash and sed so that any single digit number in the filename is buffered with a single 0, e.g. the filenames L2_error_with_G_at_2_9.csv and L2_error_with_G_at_1_16.csv would be replaced with filenames L2_error_with_G_at_02_09.csv and L2_error_with_G_at_01_16.csv. I'm seen solutions to this sort of problem that use the rename function from pearl. I don't have access to that function as I'm working on a system where I don't have installation privileges. Ideally the solution will use more of the basic features of bash, which is why I suggested a solution using sed.

EDIT: I do not need to use sed, I can use anything so long as it's a standard part of bash

Here's what I've tried

for file in L2_error_with_G_at_*.csv
do
    new=$(echo "$file" | sed 's/_\([0-9]\)/_0/g; s/_0\([0-9][0-9]\)/_\1/g;');
    mv "$file" "$new";
done;

Solution

Assumptions:

• all filenames have the same format: a_b_c_d_e_n1_n2.ext where ...
• a..e and ext do not contain white space
• n1/n2 are numbers

One bash idea:

for fname in L2_error_with_G_at_2_9.csv L2_error_with_G_at_1_16.csv
do
    printf -v new "%s_%s_%s_%s_%s_%02d_%02d.%s" ${fname//[._]/ }
    echo mv "${fname}" "${new}"
done

This generates:

mv L2_error_with_G_at_2_9.csv L2_error_with_G_at_02_09.csv
mv L2_error_with_G_at_1_16.csv L2_error_with_G_at_01_16.csv

Once the output is verified the echo can be removed from the code so that on the next run the mv occurs.

---

If the list of filenames is in a file:

while read -r fname
do
    printf -v new "%s_%s_%s_%s_%s_%02d_%02d.%s" ${fname//[._]/ }
    echo mv "${fname}" "${new}"
done < file.list

If the list of filenames is coming from a command (eg, find or ls):

while read -r fname
do
    printf -v new "%s_%s_%s_%s_%s_%02d_%02d.%s" ${fname//[._]/ }
    echo mv "${fname}" "${new}"
done < <(command that generates list of filenames)

Answered By - markp-fuso

Answer Checked By - Dawn Plyler (WPSolving Volunteer)