响铃提示命令

#!/bin/bash

ring_bell() 
{
    freq=$1; tick=$2
    # 通过频率freq算周期circ
    circ=$(echo "scale=3; 60/$freq" | bc)
    for ((i=0; i<tick; ++i)); do 
        echo -en '\a' # 响铃
        sleep $circ # 延时一个周期
    done
}

usage()
{
    echo 'Usage: ring <freq> <ticks>'
}

##########################################
if [ $# -lt 2 ]; then
    usage
    exit
fi

ring_bell $1 $2