How to compare two file names

Question

I want to compare two files in a folder and delete the number in the name which is the smaller of the two.

For instance, say the names were yearMonthDay.txt. I want to compare which is a smaller number and sudo rm it.

I know I can get the numbers via:

find *txt | awk -F'[_.]' '{ print $1}'

How then next should I compare it? Using system variables? I actually haven't used shell variables before.

Answer 1

I suggest that you make something like the following:

I made a directory with some files with 'normal' date-like names, one file with a space in the name (makes you need quoting) and one file with a new-line in the name (can cause problems, if the commands that you use assume that new-lines separate files).

$ find
.
./20210710.txt
./20200131.txt
./20210611.txt
./2020?0131.txt
./20201131.txt
./2020 131.txt

The following command line uses stat to help the find-list of txt-files,

$ find -name '*.txt' -exec stat -c '%N' {} \;
'./20210710.txt'
'./20200131.txt'
'./20210611.txt'
'./2020'$'\n''0131.txt'
'./20201131.txt'
'./2020 131.txt'

Now sort it (can be done without removing the extension)

$ find -name '*.txt' -exec stat -c '%N' {} \; | sort
'./20200131.txt'
'./20201131.txt'
'./2020 131.txt'
'./2020'$'\n''0131.txt'
'./20210611.txt'
'./20210710.txt'

and select the oldest one (at the top of the list)

$ find -name '*.txt' -exec stat -c '%N' {} \; | sort | head -n1
'./20200131.txt'

Now you can remove this file by

rm $(find -name '*.txt' -exec stat -c '%N' {} \; | sort | head -n1)

It there is a risk that there would be a space or other special character, you want to quote it (but check carefully that you avoid conflicts with previous quoting)

rm "$(find -name '*.txt' -exec stat -c '%N' {} \; | sort | head -n1)"

You can also set a variable, and use that in commands later on in a shellscript

#!/bin/bash

find -name '*.txt' -exec stat -c '%N' {} \; | sort

var1=$(find -name '*.txt' -exec stat -c '%N' {} \; | sort | head -n1)
echo '---'
read -p "Remove $var1? (y/N) " ans
if [ "$ans" == "y" ]
then
 eval rm "$var1"
fi