Shell语法

expr命令

返回的是std out 1为真 0 为假

#! /bin/bash

array=(yxc acwing lkx 1)


a=4
b=3                                                                                                                                                                          

echo "a + b = `expr $a + $b`"
echo "a - b = `expr $a - $b`"
echo "a * b = `expr $a \* $b `"
echo "a / b = `expr $a / $b`"
echo "(a + 1) * (b + 1) = `expr \( $a + 1 \) \* \( $b + 1 \)`"
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read命令

#! /bin/bash
read -p "What's your name?" -t 5 name
echo Hello, $name

echo命令

# -e 开启转义
echo -e Hello\nWorld!"   #\c是不换行

test命令

返回的是exit code 0为真 1为假

输出到文件指定文件中

 echo "Hello World" > output.txt                                                   
 echo "THE FIRST DOCUMENT" > output.txt