Shell 编程 基础
本篇主要写一些shell脚本的基础知识，编程规范。
第一个shell脚本
[root@localhost ~]# vim first.sh
#!/bin/bash
# This is first Shell Script !
cd /boot/
echo "当前所在路径："
pwd
echo "以vml为开头的文件信息："
ls -lh vml*
执行脚本
source
[root@localhost ~]# source first.sh
当前所在路径：
/boot
以vml为开头的文件信息：
-rwxr-xr-x. 1 root root 5.7M Sep 4 14:02 vmlinuz-0-rescue-ec132d04a74d4b7e828b3905a6b83437
-rwxr-xr-x. 1 root root 5.7M Aug 23 2017 vmlinuz-3.10.0-693.el7.x86_64
[root@localhost boot]#
.
[root@localhost ~]# . first.sh
当前所在路径：
/boot
以vml为开头的文件信息：
-rwxr-xr-x. 1 root root 5.7M Sep 4 14:02 vmlinuz-0-rescue-ec132d04a74d4b7e828b3905a6b83437
-rwxr-xr-x. 1 root root 5.7M Aug 23 2017 vmlinuz-3.10.0-693.el7.x86_64
[root@localhost boot]#
sh
[root@localhost ~]# sh first.sh
当前所在路径：
/boot
以vml为开头的文件信息：
-rwxr-xr-x. 1 root root 5.7M Sep 4 14:02 vmlinuz-0-rescue-ec132d04a74d4b7e828b3905a6b83437
-rwxr-xr-x. 1 root root 5.7M Aug 23 2017 vmlinuz-3.10.0-693.el7.x86_64
[root@localhost ~]#
./
[root@localhost ~]# ./first.sh
bash: ./first.sh: Permission denied
[root@localhost ~]# ls -lh first.sh
-rw-r--r--. 1 root root 139 Sep 23 22:04 first.sh
[root@localhost ~]# chmod +x first.sh
[root@localhost ~]# ls -lh first.sh
-rwxr-xr-x. 1 root root 139 Sep 23 22:04 first.sh
[root@localhost ~]# ./first.sh
当前所在路径：
/boot
以vml为开头的文件信息：
-rwxr-xr-x. 1 root root 5.7M Sep 4 14:02 vmlinuz-0-rescue-ec132d04a74d4b7e828b3905a6b83437
-rwxr-xr-x. 1 root root 5.7M Aug 23 2017 vmlinuz-3.10.0-693.el7.x86_64
符号使用
管道符 和 awk
[root@localhost ~]# grep "/bin/bash$" /etc/passwd | awk -F: '{print $1,$7}'
root /bin/bash
[root@localhost ~]# grep "/bin/bash$" /etc/passwd | awk -F":" '{print $1,$7}'
root /bin/bash
[root@localhost ~]# df -hT | grep "/$" | awk '{print $1,$6}'
/dev/sda2 21%
[root@localhost ~]# df -hT | grep "/$" | awk -F" " '{print $1,$6}'
/dev/sda2 21%
重定向输出
[root@localhost ~]# echo "123" > test.txt
[root@localhost ~]# cat test.txt
123
[root@localhost ~]# echo "456" >> test.txt
[root@localhost ~]# cat test.txt
123
456
重定向输入
[root@localhost ~]# rm test.txt
rm: remove regular file ‘test.txt’? ^C
[root@localhost ~]# echo "y" > temp.txt
[root@localhost ~]# ls te*
temp.txt test.txt
[root@localhost ~]# rm test.txt < temp.txt
rm: remove regular file ‘test.txt’? [root@localhost ~]#
[root@localhost ~]# ls te*
temp.txt
错误重定向
- 混合输出
[root@localhost ~]# tar zcvf opt.tar.gz /opt/ &> error.log
[root@localhost ~]# cat error.log
tar: Removing leading `/' from member names
/opt/
/opt/rh/
- 标准错误输出
[root@localhost ~]# tar zcvf opt.tar.gz /opt/ 2> error.log
/opt/
/opt/rh/
[root@localhost ~]# cat error.log
tar: Removing leading `/' from member names
[root@localhost ~]# tar zcvf opt.tar.gz /opt/ 2>> error.log
/opt/
/opt/rh/
[root@localhost ~]# cat error.log
tar: Removing leading `/' from member names
tar: Removing leading `/' from member names
变量
定义、查看变量
[root@localhost ~]# Product=java
[root@localhost ~]# Version=1.8
[root@localhost ~]# echo $Product
java
[root@localhost ~]# echo $Product $Version
java 1.8
大括号
[root@localhost ~]# echo $Product1.8
.8
[root@localhost ~]# echo ${Product}1.8
java1.8
引号
[root@localhost ~]# echo "java $Version"
java 1.8
[root@localhost ~]# echo 'java $Version'
java $Version
反撇号
[root@localhost ~]# which cat
/usr/bin/cat
[root@localhost ~]# ls -lh /usr/bin/cat
-rwxr-xr-x. 1 root root 53K Nov 6 2016 /usr/bin/cat
[root@localhost ~]# ls -lh `which cat`
-rwxr-xr-x. 1 root root 53K Nov 6 2016 /usr/bin/cat
read
[root@localhost ~]# read -p "请输入一个整数：" num
请输入一个整数：10
[root@localhost ~]# echo $num
10
变量作用范围
- 设置局部变量为全局变量
[root@localhost ~]# echo $Product $Version
java 1.8
[root@localhost ~]# bash
[root@localhost ~]# echo $Product $Version
[root@localhost ~]# exit
[root@localhost ~]# export Product Version
[root@localhost ~]# bash
[root@localhost ~]# echo $Product $Version
java 1.8
- 直接定义全局变量
[root@localhost ~]# export num=100
[root@localhost ~]# echo $num
100
[root@localhost ~]# bash
[root@localhost ~]# echo $num
100
数值变量的运算
[root@localhost ~]# num1=8
[root@localhost ~]# num2=5
[root@localhost ~]# expr $num1 + $num2
13
[root@localhost ~]# expr $num1 - $num2
3
[root@localhost ~]# expr $num1 \* $num2
40
[root@localhost ~]# expr $num1 / $num2
1
[root@localhost ~]# expr $num1 % $num2
3
- Demo
[root@localhost ~]# vim suanshu.sh
#!/bin/bash
read -p "请输入第1个数字：" num1
read -p "请输入第2个数字：" num2
result1=`expr $num1 + $num2`
result2=`expr $num1 - $num2`
result3=`expr $num1 \* $num2`
result4=`expr $num1 / $num2`
result5=`expr $num1 % $num2`
echo "加法：$num1 + $num2 = $result1"
echo "减法：$num1 - $num2 = $result2"
echo "乘法：$num1 * $num2 = $result3"
echo "除法：$num1 / $num2 = $result4"
echo "取余：$num1 % $num2 = $result5"
[root@localhost ~]# chmod +x suanshu.sh
[root@localhost ~]# ./suanshu.sh
请输入第1个数字：8
请输入第2个数字：5
加法：8 + 5 = 13
减法：8 - 5 = 3
乘法：8 * 5 = 40
除法：8 / 5 = 1
取余：8 % 5 = 3
特殊变量
环境变量
[root@localhost ~]# env
位置变量
[root@localhost ~]# vim suanshu.sh
#!/bin/bash
echo "第一个位置变量值为：$1"
echo "第二个位置变量值为：$2"
result1=`expr $1 + $2`
result2=`expr $1 - $2`
result3=`expr $1 \* $2`
result4=`expr $1 / $2`
result5=`expr $1 % $2`
echo "加法：$1 + $2 = $result1"
echo "减法：$1 - $2 = $result2"
echo "乘法：$1 * $2 = $result3"
echo "除法：$1 / $2 = $result4"
echo "取余：$1 % $2 = $result5"
[root@localhost ~]# chmod +x suanshu.sh
[root@localhost ~]# ./suanshu.sh 8 5
第一个位置变量值为：8
第二个位置变量值为：5
加法：8 + 5 = 13
减法：8 - 5 = 3
乘法：8 * 5 = 40
除法：8 / 5 = 1
取余：8 % 5 = 3
预定义变量
[root@localhost ~]# vim suanshu.sh
#!/bin/bash
echo "第一个位置变量值为：$1"
echo "第二个位置变量值为：$2"
result1=`expr $1 + $2`
result2=`expr $1 - $2`
result3=`expr $1 \* $2`
result4=`expr $1 / $2`
result5=`expr $1 % $2`
echo "加法：$1 + $2 = $result1"
echo "减法：$1 - $2 = $result2"
echo "乘法：$1 * $2 = $result3"
echo "除法：$1 / $2 = $result4"
echo "取余：$1 % $2 = $result5"
echo "执行的脚本名称：$0"
echo "执行的参数个数：$#"
echo "执行的参数内容：$*"
[root@localhost ~]# chmod +x suanshu.sh
[root@localhost ~]# ./suanshu.sh 8 5
第一个位置变量值为：8
第二个位置变量值为：5
加法：8 + 5 = 13
减法：8 - 5 = 3
乘法：8 * 5 = 40
除法：8 / 5 = 1
取余：8 % 5 = 3
执行的脚本名称：./suanshu.sh
执行的参数个数：2
执行的参数内容：8 5
[root@localhost ~]# echo $?
0
