What are the common special symbols in bash

This article shows you what common special symbols in bash, which are concise and easy to understand, can definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

Simple special characters

!: the most direct function is logical non, and the most commonly used function is the operation history command (note that this function cannot be used in shell programming). For example, *! Execute the previous command,! $refers to the last word of the previous command, and! # * * refers to the entire command executed. For more information, please refer to: bash shortcut key arrangement

The most direct function is the expression delimiter, which is commonly used in * * {} for parameter substitution * *, a comma for lowercase and two commas for all lowercase (added in bash version 4.0):

Var=FooBarecho ${var,} / the result is fooBarecho ${var,} / / the result is foobar

.: the most common function is the current directory, the useful function is to replace the source command, and other functions include any character in the regular expression

:: null command (returns 0). It is also often used as a delimiter in environment variables such as PATH. The magical function is that it can be used as a function name.

;: command separator

~: user home directory, instead of $HOME environment variable

#: comment symbol, which is also a string truncation

&: let the program be executed in the background, which can be used alone, and often cooperate with nohup to make the program separate from the current terminal.

/: folder delimiter, which represents the root directory alone, and is also a division sign

*: the most commonly used is to match wildcards, which is also the multiplication sign

\: escape or wrap

-: common functions are command short options, such as ls-ah; utility is used alone to represent the previous directory, and to replace standard input and output; it is also a minus sign

+: is often used in regular expressions to indicate at least one match, which is also a plus sign

| |: pipeline |

Match one character, or 0-1 matches in a regular expression, is also a ternary operator

..: superior directory