dotfiles/.local/bin/statusbar/sb-nettraf

#!/bin/sh
update() {
    sum=0
    for arg; do
        read -r i < "$arg"
        sum=$(( sum + i ))
    done
    cache=/tmp/${1##*/}
    [ -f "$cache" ] && read -r old < "$cache" || old=0
    printf %d\\n "$sum" > "$cache"
    printf %d\\n $(( sum - old ))
}
rx=$(update /sys/class/net/[ew]*/statistics/rx_bytes)
tx=$(update /sys/class/net/[ew]*/statistics/tx_bytes)
printf "%5sB %5sB\\n" $(numfmt --to=iec $rx $tx)