shell脚本-03
循环结构
1、循环开始的条件
2、循环操作
3、循环终止的条件
shell语言
for, while, util
for循环
语法：
for 变量 in 取值列表; do
statement
statement
done
for 变量 in 取值列表
do
statement
statement
done
取值列表：
数字
10 20 30
使用seq命令生成数字的序列
seq 10
seq 3 10
seq 1 2 10
字符
aa bb cc
文件
编写脚本，计算1---100的和
!/bin/bash
sum=0
for i in seq 100; do
let sum=$sum+$i
done
echo $sum
编写脚本，计算1--100所有奇数的和
!/bin/bash
sum=0
for i in seq 100; do
let ys=$i%2
if [ $ys -ne 0 ]; then
let sum=$sum+$i
fi
done
echo $sum
编写脚本，实现批量创建用户user1...user10
!/bin/bash
for i in seq 10; do
if ! id user$i &> /dev/null; then
useradd user$i
echo "redhat" | passwd --stdin user$i &> /dev/null
echo "用户user$i创建完成，初始密码为redhat"
else
echo "用户user$i已经存在"
fi
done
编写脚本，检测172.16.20.0/24在线主机IP
!/bin/bash
network=172.16.20.
for i in seq 254; do
if ping -c 1 -W 1 $network$i &> /dev/null; then
echo "Host $network$i is up"
fi
done
启动多线程：
!/bin/bash
network=172.16.80.
for i in seq 254; do
{
if ping -c 1 -W 1 $network$i &> /dev/null; then
echo "Host $network$i is up"
fi
}&
done
wait
以字符作为取值列表
!/bin/bash
for name in alice natsha kira merry; do
useradd $name
echo "$name create finished."
done
以文件作为取值列表
`cat FILE`
编写脚本，向系统中所有用户打招呼
!/bin/bash
for i in awk -F: '{print $1}' /etc/passwd; do
echo "Hello, $i"
done
编写脚本， 将某目录下所有以.txt结尾的文件改为以.mp3结尾
!/bin/bash
for i in ls -l /tmp/test | grep "txt$" | awk '{print $9}'; do
file_name=echo $i | awk -F. '{print $1}'
mv /tmp/test/$i /tmp/test/$file_name.mp3
done
编写脚本, 分别统计/bin/bash和/sbin/nologin用户的个数
!/bin/bash
bash_number=0
nologin_number=0
line=$(wc -l /etc/passwd | awk '{print $1}')
for i in seq $line; do
sh_name=$(head -n $i /etc/passwd | tail -1 | awk -F: '{print $7}')
case $sh_name in
/sbin/nologin)
let nologin_number=$nologin_number+1
;;
/bin/bash)
let bash_number=$bash_number+1
;;
esac
done
echo "shell为/bin/bash的：$bash_number"
echo "shell为/sbin/nologin的：$nologin_number"
编写脚本，检测172.16.0.0/16网段的在线主机
172.16.0.1 ---------- 172.16.0.255
172.16.1.1 ---------- 172.16.1.255
172.16.2.1 ---------- 172.16.2.255
...
172.16.254.1 -------- 172.16.254.255
for i in `seq 10`;
for j in `seq 10`; i=1, j=1,j=10 i=2, j=1..10
编写脚本，显示九九乘法表
编写脚本，编译安装apache
中断循环的语句
break 中断整体循环
continue 中断本次循环
break用法：
!/bin/bash
sum=0
for i in seq 100; do
let sum=$sum+$i
if [ $sum -ge 3000 ]; then
echo $i
break
fi
done
continue用法：
!/bin/bash
sum=0
for i in seq 100; do
let ys=$i%2
if [ $ys -eq 0 ]; then
continue
fi
let sum=$sum+$i
done
echo $sum
编写脚本，列出系统中shell为/bin/bash的前5个用户名
!/bin/bash
number=0
line=$(wc -l /etc/passwd | awk '{print $1}')
for i in seq $line; do
sh_name=head -n $i /etc/passwd | tail -1 | awk -F: '{print $7}'
if [ $sh_name == "/bin/bash" ]; then
name=head -n $i /etc/passwd | tail -1 | awk -F: '{print $1}'
echo -n "$name "
let number=$number+1
if [ $number -eq 5 ]; then
break
fi
fi
done
echo
while循环
while CONDITION; do
statement
statement
<改变循环条件真假的语句>
done
编写脚本，计算1---100的和
!/bin/bash
sum=0
i=1
while [ $i -le 100 ]; do
let sum=$sum+$i
let i=$i+1
done
echo $sum
while true; do
statement
statement
done
!/bin/bash
while true; do
read -p "请输入你的选择：" choice
if [ $choice == "q" ]; then
break
fi
done
!/bin/bash
while true; do
uptime
sleep 3
done
while read line; do
statement
statement
done < file
!/bin/bash
bash_num=0
nologin_num=0
while read line; do
sh_name=$(echo $line | awk -F: '{print $7}')
case $sh_name in
/bin/bash)
let bash_num=$bash_num+1
;;
/sbin/nologin)
let nologin_num=$nologin_num+1
;;
esac
done < /etc/passwd
echo $bash_num
echo $nologin_num
util循环：
util CONDITION; do
statement
statement
done
条件为假时，执行循环，条件为真时，结束循环
链接: https://pan.baidu.com/s/1kU8jXqR 密码: ryxe