Rote memorization in the shell

One, the shell quotes

1. "", double quotation marks (do not retain the full content, such as encountered $, anti-quotes, \ etc will execute the corresponding shell)

echo "Today is `date`"   -> Today is Wed Aug  

2. Single quotation mark (full retention content)

echo "Today is `date`"   -> Today is `date`  

3. "Anti-quotation mark (the shell inside the inverted quote will execute)

echo `date`   -> Wed Aug 3 05:59:19 GMT 2011  

Second, the shell variable description

$$Shell本身的PID（ProcessID）$!Shell最后运行的后台Process的PID$?最后运行的命令的结束代码（返回值）$-使用Set命令设定的Flag一览$*所有参数列表。如"$*"用 "" 括起来的情况、以"$1 $2 … $n"的形式输出所有参数。[email protected]所有参数列表。如"[email protected]"用 "" 括起来的情况、以"$1" "$2" … "$n" 的形式输出所有参数。$#添加到Shell的参数个数$0Shell本身的文件名$1～$n添加到Shell的各参数值。$1是第1参数、$2是第2参数

A simple script can explain the meaning of each variable.

#!/bin/shecho "number:$#"echo "scname:$0"echo "first :$1"echo "second:$2"echo "argume:[email protected]"

Output:

number:2scname:./variablefirst: aasecond:bbargume:aa bb

By displaying the results you can see:
$# is the number of arguments passed to the script
The name of the script itself
$ $ is the first parameter passed to the shell script
$ $ is the second parameter passed to the shell script
[Email protected] is a list of all parameters passed to the script

Attach a Vim learning guide

Https://coolshell.cn/articles/5426.html

Rote memorization in the shell