Linux Shell脚本编程while语句
2024-09-07 17:21:49
Linux Shell脚本编程while语句案例
1,每隔3秒,打印一次系统负载
#!/bin/bash
while true
do
uptime
sleep 3
done
do
uptime
sleep 3
done
2,把监控结果保存到文件,在后台执行,然后用tail -f监控文件变化
ghostwu@dev:~/linux/shell/flow_control$ sh while.sh &
[1] 12867
ghostwu@dev:~/linux/shell/flow_control$ sh while.sh &
[1] 12867
#!/bin/bash
while true
do
uptime >> log.txt
sleep 3
done
do
uptime >> log.txt
sleep 3
done
ghostwu@dev:~/linux/shell/flow_control$ tail -f log.txt
06:14:32 up 33 min, 1 user, load average: 0.33, 0.35, 0.32
06:14:35 up 33 min, 1 user, load average: 0.33, 0.35, 0.32
06:14:38 up 33 min, 1 user, load average: 0.31, 0.34, 0
...
3,进程调度相关命令
fg: 把当前脚本或者任务放到前台执行。如果指定某个任务:fg 任务编号。 任务编号通过jobs查询
bg: 把任务放到后台执行
jobs:查看当前执行的脚本或者任务
ctrl+z:暂停执行当前的脚本
sh while1.sh & : 加上&,表示后台执行脚本
06:14:32 up 33 min, 1 user, load average: 0.33, 0.35, 0.32
06:14:35 up 33 min, 1 user, load average: 0.33, 0.35, 0.32
06:14:38 up 33 min, 1 user, load average: 0.31, 0.34, 0
...
3,进程调度相关命令
fg: 把当前脚本或者任务放到前台执行。如果指定某个任务:fg 任务编号。 任务编号通过jobs查询
bg: 把任务放到后台执行
jobs:查看当前执行的脚本或者任务
ctrl+z:暂停执行当前的脚本
sh while1.sh & : 加上&,表示后台执行脚本
ghostwu@dev:~/linux/shell/flow_control$ fg
sh while.sh
^Z
[1]+ Stopped sh while.sh
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]+ Stopped sh while.sh
ghostwu@dev:~/linux/shell/flow_control$ bg
[1]+ sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]+ Running sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ sh while.sh &
[2] 13411
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]- Running sh while.sh &
[2]+ Running sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ fg
sh while.sh
^Z
[2]+ Stopped sh while.sh
ghostwu@dev:~/linux/shell/flow_control$ bg
[2]+ sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]- Running sh while.sh &
[2]+ Running sh while.sh &
sh while.sh
^Z
[1]+ Stopped sh while.sh
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]+ Stopped sh while.sh
ghostwu@dev:~/linux/shell/flow_control$ bg
[1]+ sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]+ Running sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ sh while.sh &
[2] 13411
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]- Running sh while.sh &
[2]+ Running sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ fg
sh while.sh
^Z
[2]+ Stopped sh while.sh
ghostwu@dev:~/linux/shell/flow_control$ bg
[2]+ sh while.sh &
ghostwu@dev:~/linux/shell/flow_control$ jobs
[1]- Running sh while.sh &
[2]+ Running sh while.sh &
4,用while循环打印0, 1, 2, 3, 4
#!/bin/bash
i=0
while [ $i -lt 5 ]
do
echo $i
(( i++ ))
done
i=0
while [ $i -lt 5 ]
do
echo $i
(( i++ ))
done
两个中括号也可以
#!/bin/bash
i=0
while [[ $i -lt 5 ]]
do
echo $i
(( i++ ))
done
i=0
while [[ $i -lt 5 ]]
do
echo $i
(( i++ ))
done
还可以用计算表达式
#!/bin/bash
i=0
while (( i < 5 ))
do
echo $i
(( i++ ))
done
i=0
while (( i < 5 ))
do
echo $i
(( i++ ))
done
5,计算1....100的和
ghostwu@dev:~/linux/shell/flow_control$ sh sum.sh
1+2+3..+100=5050
ghostwu@dev:~/linux/shell/flow_control$ cat sum.sh
#!/bin/bash
1+2+3..+100=5050
ghostwu@dev:~/linux/shell/flow_control$ cat sum.sh
#!/bin/bash
i=1
while (( i <= 100 ))
do
(( sum = sum + i ))
(( i++ ))
done
echo "1+2+3..+100="${sum}
while (( i <= 100 ))
do
(( sum = sum + i ))
(( i++ ))
done
echo "1+2+3..+100="${sum}
6,猜数字
#!/usr/bin/bash
sum=$((RANDOM%51))
echo "需要你猜的数是:"$sum
sleep 1
echo "请输入1-50之间的数,开始猜吧!"
count=0
function type_num(){
read -p "请输入一个数吧:" n
expr $n + 1 &>/dev/null
if [ $? -ne 0 ]; then
echo "请输入一个数字"
type_num
fi
}
read -p "请输入一个数吧:" n
expr $n + 1 &>/dev/null
if [ $? -ne 0 ]; then
echo "请输入一个数字"
type_num
fi
}
function guess(){
(( count++ ))
if [ $n -eq $sum ]; then
echo "你猜中了,你的次数是:"${count}
if [ $count -lt 3 ]; then
echo "你太厉害了"
elif [ $count -ge 3 -a $count -lt 6 ]; then
echo "还是不错的,加油"
else
echo "你有点水啊"
fi
exit 0
elif [ $n -gt $sum ]; then
echo "猜大了"
type_num
else
echo "猜小了"
type_num
fi
}
(( count++ ))
if [ $n -eq $sum ]; then
echo "你猜中了,你的次数是:"${count}
if [ $count -lt 3 ]; then
echo "你太厉害了"
elif [ $count -ge 3 -a $count -lt 6 ]; then
echo "还是不错的,加油"
else
echo "你有点水啊"
fi
exit 0
elif [ $n -gt $sum ]; then
echo "猜大了"
type_num
else
echo "猜小了"
type_num
fi
}
function main(){
type_num
while true
do
guess
done
}
type_num
while true
do
guess
done
}
main
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