This bash script is to list all the custom fields in the system as CustomField doesn't support wildcard

ListAllCustomFields.sh

#!/bin/bash
extensionsToExclude=(
     'History'
     '__History'
     'Share'
     '__Share'
     'ChangeEvent'
     '__ChangeEvent'
   )
input="ObjNames.csv"
rm CustomFields.txt
touch CustomFields.txt
while IFS= read -r objName
do
    echo $objName
    excludeObject=false
    for objExt in "${extensionsToExclude[@]}"
    do
        if [[ $objName == *"$objExt" ]]; then
            echo "Skipping $objName"
            excludeObject=true
            break
        fi
    done
    if [[ $excludeObject == false ]]; then
        echo "proceeding with $objName"
        sfdx force:schema:sobject:describe --targetusername=prod --sobjecttype=$objName --json | jq -r --arg objName $objName '.result.fields[] | $objName + "." + .name' >> CustomFields.txt
    fi
done < "$input"