#!/usr/bin/bash
ip=115.239.210.27

if ping -c1 $ip &>/dev/null ;then    # &>/dev/null: output of ping $ip is null
    echo "$ip is up."
else
    echo "$ip is down."
fi

#!/usr/bin/bash
read ip

ping -c1 $ip &>/dev/null
if [ $? -eq 0 ]; then
    echo "$ip is up."
else
    echo "$ip is down."
fi

#!/bin/bash
                       
ping -c1 $1 &>/dev/null
if [ $? -eq 0 ]; then
    echo "$1 is up."   
else
    echo "$1 is down." 
fi

#!/bin/bash
echo "the par of 2: $2"
echo "the par of 1: $1"
echo "the par of 4: $4"

echo "all par: $*"     
echo "all par: $@"     
echo "the num of par: $#"
echo "the PID of cur process: $$"
  
echo '$1='$1           
echo '$2='$2           
echo '$3='$3           
echo '$*='$*           
echo '$@='$@           
echo '$#='$#
echo '$$='$$ 

#!/bin/bash
# if user have no parma
if [ $# -eq 0 ]; then  
    echo "usage: `basename $0` file"
fi


if [ ! -f $1 ]; then     # not a file
    echo "erro file!"  
fi
  
echo "ping........."   
  
for ip in `cat $1`     
do
    ping -c1 $ip &>/dev/null
    if [ $? -eq 0 ];then    
        echo "$ip is up."       
    else
        echo "$ip is down."     
    fi
done

echo "ip1 is $ip1"
echo "ip2 is $ip2"

#! /bin/bash

pwd
ls

DATA=$(date)

echo $DATA

$(curl www.itcast.cn > 1.html)

pwd

echo "scale=3;6/4" |bc

awk 'BEGIN{print 1/2}'