GhostScript PDF compression of a folder and all the subfolders with multithreading (using screen)

README.MD

(Install ghostscript and screen depends on your distro here for debian/ubuntu)

apt install -y screen ghostscript

Firstly change the path where your files are by changning the line files='/home/poli/test

Then you can simply do a chmod +x on both files (they need to be in the same directory) and run

./pdfCompress.sh

To download both scripts run wget https://gist.githubusercontent.com/IIPoliII/dfe302965ef780caec7bf94ef0eac887/raw/6c401c3b95165c4a6e4332e227eb70f63aa00f98/GSCompress.sh && wget https://gist.githubusercontent.com/IIPoliII/dfe302965ef780caec7bf94ef0eac887/raw/6c401c3b95165c4a6e4332e227eb70f63aa00f98/pdfCompress.sh

or simply download both files manually

GSCompress.sh

#!/bin/bash
#Variable for choosing the file

FileInput=$1
FileOutput=$2
#GS compression of the pdf

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/default -dNOPAUSE -dBATCH -dDetectDuplicateImages -dCompressFonts=true -r300 -sOutputFile="$FileOutput" "$FileInput"

mv "$FileOutput" "$FileInput"

pdfCompress.sh

#!/bin/bash
# Created the 11.11.2019 using ghostscript

#Where to serach the file

files='/home/poli/test'

#Needed variables

count=1
seconds=0

#Remove the tmp folder in case it still exsits

rm -rf /tmp/GSCompressing

#Map all folders to an array

mapfile -t FoldersList < <(find $files -type f -name '*.pdf' | sed 's%/[^/]*$%/%' | awk '!a[$0]++')

for Folder in "${FoldersList[@]}"
        do

                #Map all the files of the folder to an array

                mapfile -t FilesList < <(find $Folder -maxdepth 1 -type f -name '*.pdf' | sed "s/'/\\\'/")

                #Create a temporary directory

                mkdir /tmp/GSCompressing

                #Loop trought array to compress each files

                for File in "${FilesList[@]}"
                do
                        #Put only the file name in the variable

                        FileName=`echo "$File" | sed 's|.*/||'`

                        #Launch a screen compressing the PDF's

                        screen -dmS GSCompress${count} ./GSCompress.sh "$File" "/tmp/GSCompressing/${FileName}"

                        echo "Compressing the PDF : $File"

                        let "count++"
                done

                #Now we wait until the screens are finished so we can assume the pdf are compressed

                screenls=$(screen -ls)

                #We check if any screen is still on

                while [[ $screenls == *GSCompress* ]]
                        do
                                screenls=$(screen -ls)

                                let "seconds++"

                                echo -ne "Checking if ghostscript is still compressing : $seconds"\\r

                                sleep 1s
                        done

                seconds=0

                rm -rf /tmp/GSCompressing

        done
#This echo is to prevent to return on the same line as the \\r does

echo ""

echo "All PDFS were compressed"