shell脚本以 .sh为后缀，里面存放着一行行要运行的linux指令。

shell脚本第一行一定为 #!/bin/bash，表示使用bash。

shell文件举例如下：

#!/bin/bash

echo "hello shell!"

shell文件默认没有可执行权限，因此 chmod 777 myshell.sh

./myshell.sh

交互式shell

#!/bin/bash

echo "Please input your name: "

read name

echo "I have read your name" $name

read -p "Please input your name and height: " age height

echo "Your age is $age, your height is $height"

上述代码中，read用于读取变量，-p 用于输出提示信息

shell支持整型变量的运算

#!/bin/bash

echo "Please input two int nums: "

read -p "First num: " a

read -p "Second num: " b

total=$(($a + $b))

echo "$a + $b = $total"

运算表达式要用双重括号

total后的"="两边不能有空格

test命令的使用

1. 判断文件是否存在

#!/bin/bash

echo "Please input filename: "

read -p "File name: " filename

test -e $filename && echo "$filename exist!" || echo "$filename does not exist!"   

2. 判断字符串是否相等

#!/bin/bash

echo "Please input two strings: "

read -p "First string: " firststr

read -p "Second string: " second

test $firststr == $secondstr && echo "Equal" || echo "Not equal"

[ ] 判断符作用类似于test，里面只能使用==或!=

#!/bin/bash

echo "Please input two strings: "

read -p "First string: " firststr

read -p "Second string: " second

[ "$firststr" == "$secondstr" ] && echo "Equal" || echo "Not equal"

以上红色为空格，且变量两端要加双引号