#!/bin/bash
IF=wlp3s0
TMPFILE=/tmp/tmux_net_speed.txt

# 初始化上一秒流量
read RX_PREV TX_PREV <<< $(awk -v iface=$IF '$1 ~ iface {print $2, $10}' /proc/net/dev)

while true; do
    sleep 1
    read RX_CUR TX_CUR <<< $(awk -v iface=$IF '$1 ~ iface {print $2, $10}' /proc/net/dev)
    RX_RATE=$(( (RX_CUR - RX_PREV)/1024 ))
    TX_RATE=$(( (TX_CUR - TX_PREV)/1024 ))
    printf "↑%dKB/s ↓%dKB/s" $TX_RATE $RX_RATE > $TMPFILE
    RX_PREV=$RX_CUR
    TX_PREV=$TX_CUR
done