a shell script to copy the `Icons` folder out of an IconFactory archive DMG download, based on https://stackoverflow.com/a/48251635

dmg_extract.sh

#!/bin/bash

dmg_path="$1"

# use process redirection to capture the mount point and dev entry
IFS=$'\n' read -rd '\n' mount_point dev_entry < <(
    # mount the diskimage; leave out -readonly if making changes to the filesystem
    hdiutil attach -readonly -plist "$dmg_path" | \

    # convert output plist to json
    plutil -convert json - -o - | \

    # extract mount point and dev entry
    jq -r '
        .[] | .[] |
        select(."volume-kind" == "hfs") |
        ."mount-point" + "\n" + ."dev-entry"
    '
)

collection_name=${mount_point//\/Volumes\///}

echo "Copying $collection_name..."
cp -rp "$mount_point/Icons" "/Users/ian/Desktop/icons/$collection_name"

# unmount the disk image
hdiutil detach "$dev_entry"

I ran this on a whole pile of downloads via $ for i in {1..57}; do ./dmgextract.sh ~/Downloads/download-$i.dmg; done

It choked on a couple of the downloads: cp: /Volumes/Weyland Corp - Mac/Icons: No such file or directory but its easy to catch any stragglers manually.