Asterisks represent any character, such as *.txt
？ Represents any one character
: Represents a delimiter for different commands
#代表配置文件的注释
| Represents a pipeline
~ Represents the user's home directory
-Represents the last catalog
$ variable content in front of $ output variable
/path delimiter, also representing the root
' > ' or 1> output redirection, overwriting the original data
' >> ' or 2>> append output redirection.
< input redirection
<< Append input Redirection
' Single quotes, no variable substitution function, output WYSIWYG
"'" double quotes with variable displacement function, such as echo " date " will show time
' Anti-quotes, two anti-quotes in the middle for the command to be executed first, equivalent to $ (),
The middle of {} is a command block combination or a content sequence
！ In logical operators, non-
|| In the logical operator or
&& in logical operators
.. A dot represents the current directory
.. Two points representing the previous level of the directory
Linux wildcard characters
