The accumulation of some small knowledge of scripts in Linux

For a variable problem:

Assign a value to the variable, a= "Hello World", and now print the contents of variable A: echo $a.

For the use of ${}: Like $aall, we want $ A, which is, you can ${a}all.

For the difference between $ () and ${}: $ () is the result of executing the code inside, and ${} is the parameter, {} is to avoid the subsequent effects, such as the parameter ${a}a to be used in a coherent way. If you do not use {}, the system will be recognized as $AA.

$# 是传给脚本的参数个数

$0是脚本本身的名字

$1是传递给该shell脚本的第一个参数

$2是传递给该shell脚本的第二个参数

[email protected] 是传给脚本的所有参数的列表

$* 是以一个单字符串显示所有向脚本传递的参数，与位置变量不同，参数可超过9个

$$ 是脚本运行的当前进程ID号

$? 是显示最后命令的退出状态，0表示没有错误，其他表示有错误

PWD command:

The accumulation of some small knowledge of scripts in Linux