Bash - how to copy latest files by filename to another folder?

Question

Let's say I have these files in folder Test1

AAAA-12_21_2020.txt
AAAA-12_20_2020.txt
AAAA-12_19_2020.txt
BBB-12_21_2020.txt
BBB-12_20_2020.txt
BBB-12_19_2020.txt

I want below latest files to folder Test2

AAAA-12_21_2020.txt
BBB-12_21_2020.txt

We encourage questioners to show what they have tried so far to solve the problem themselves. — Cyrus, Jan 01 '21 at 16:12

veprolet · Answer 1 · 2021-01-01T17:28:10.520

This code would work:

ls $1 -U | sort | cut -f 1 -d "-" | uniq | while read -r prefix; do
    ls $1/$prefix-* | sort -t '_' -k3,3V -k1,1V -k2,2V | head -n 1
done

We first iterate over every prefix in the directory specified as the first argument, which we get by sorting the list of files and deleting duplicates, before extracting everything before -. Then we sort those filenames by three fields separated by the _ symbol using the -k option of sort (primarily by years in the third field, then months in second and lastly days). We use version sort to be able to ignore the text around and interpret numbers correctly (as opposed to lexicographical sort).

I'm not sure whether this is the best way to do this, as I used only basic bash functions. Because of the date format and the fact that you have to differentiate prefixes, you have to parse the string fully, which is a job better suited for AWK or Perl.

Nonetheless, I would suggest using day-month-year or year-month-day format for machine-readable filenames.

O_O I never knew sort had a `-t` field separator option and always did acrobatics with `cut` instead — Michael Berkowski, Jan 01 '21 at 17:20
You should avoid the `for i in $(cmd)` syntax and use `cmd|while read` instead. Here is why: https://stackoverflow.com/a/19607361/2900196 — Idriss Neumann, Jan 01 '21 at 17:23
@IdrissNeumann Thank you. You are absolutely right. I wouldn't handle whitespace correctly. I updated my answer. — veprolet, Jan 01 '21 at 17:29

Idriss Neumann · Answer 2 · 2021-01-01T17:24:51.107

1

Using awk:

ls -1 Test1/ | awk -v src_dir="Test1" -v target_dir="Test2" -F '(-|_)' '{p=$4""$2""$3; if(!($1 in b) || b[$1] < p){a[$1]=$0}} END {for (i in a) {system ("mv "src_dir"/"a[i]" "target_dir"/")}}'

edited Jan 01 '21 at 17:24

answered Jan 01 '21 at 17:17

Idriss Neumann

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Bash - how to copy latest files by filename to another folder?

2 Answers2