Bash – a faster way to extract the year from file names to move them to year based directories than the current approach of using `cut` and `rev`

bashcut

I have a web application that access a remote storage running Linux to get some files, the problem is that the remote storage have currently 3 million files , so accessing the normal way is a bit tricky.

So I needed to work on a script that is going to make it a little bit more easy to use , this script is going to reorganize the files into multiple folders depending on their creation date and specially their names,i made the script and it worked just fine, it intended to do what it meant to do, but it was too slow, 12 hours to perform the work completely (12:13:48 to be precise).

I think that the slowness is coming from the multiple cut and rev calls I make.

example :

I get the file names with an ls command that I loop into with for, and for each file I get the parent directory and, depending on the parent directory, I can get the correct year:

 case "$parent" in
                ( "Type1" )
                year=$(echo "$fichier" | rev | cut -d '_' -f 2 | rev );;

                ( "Type2" )
                year=$(echo "$fichier" | rev | cut -d '_' -f 2 | rev);;

                ( "Type3" )
                year=$(echo "$fichier" | rev | cut -d '_' -f 1 | rev | cut -c 1-4);;

                ( "Type4" )
                year=$(echo "$fichier" | rev | cut -d '_' -f 1 | rev | cut -c 1-4);;

                ( "Type5" )
                year=$(echo "$fichier" | rev | cut -d '_' -f 1 | rev | cut -c 1-4);;
                esac

for type1 of files :

the file==>MY_AMAZING_FILE_THAT_IMADEIN_YEAR_TY.pdf

I need to get the year so I perform a reverse cut:

year=$(echo "$file" | rev | cut -d '_' -f 2 | rev );;

for type2 of files :

the file==>MY_AMAZING_FILE_THAT_IMADE_IN_YEAR_WITH_TY.pdf

etc…

and then I can mv the file freely : mv $file /some/path/destination/$year/$parent

and yet this is the simplest example, there are some files that are much more complex, so to get 1 information I need to do 4 operations, 1 echo , 2rev and 1echo.

While the script is running I am getting speeds of 50 files/sec to 100 files\s , I got this info by doing a wc-l output.txt of the script.

Is there anything I can do to make it faster? or another way to cut the files name? I know that I can use sed or awk or string operations but I did not really understand how.

Best Answer

To get the YEAR portion of the filename MY_AMAZING_FILE_THAT_IMADEIN_YEAR_TY.pdf without using external utilities:

name='MY_AMAZING_FILE_THAT_IMADEIN_YEAR_TY.pdf'

year=${name%_*}    # remove everything after the last '_'
year=${year##*_}   # remove everything up to the last (remaining) '_'

After update to the question:

Moving PDF files from under topdir to a directory /some/path/destination/<year>/<parent> where <year> is the year found in the filename of the file, and <parent> is the basename of the original directory that the file was found in:

find topdir -type f -name '*.pdf' -exec bash ./movefiles.sh {} +

movefiles.sh is a shell script in the current directory:

#!/bin/bash

destdir='/some/path/destination'

for name; do
    # get basename of directory
    parent=${name%/*}
    parent=${parent##*/}

    # get the year from the filename:
    #  - Pattern:  _YYYY_         (in the middle somewhere)
    #  - Pattern:  _YYYYMMDD.pdf  (at end)
    if [[ "$name" =~ _([0-9]{4})_ ]] ||
       [[ "$name" =~ _([0-9]{4})[0-9]{4}\.pdf$ ]]; then
        year="${BASH_REMATCH[1]}"
    else
        printf 'No year in filename "%s"\n' "$name" >&2
        continue
    fi

    # make destination directory if needed
    # (remove echo when you have tested this at least once)
    if [ ! -d "$destdir/$year/$parent" ]; then
        echo mkdir -p "$destdir/$year/$parent"
    fi

    # move file
    # (remove echo when you have tested this at least once)
    echo mv "$name" "$destdir/$year/$parent"
done
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