Shell substitution: Shell variable substitution, command substitution, escape character

If the expression contains special characters, the Shell will replace it. For example, using a variable in double quotes is a substitution, and an escape character is also a substitution.

As an example:

1. #!/bin/bash
2. a = Ten
3. Echo-e "Value of A is $a \ n"

Operation Result:

Value of A is 10

here-e indicates the substitution of the escape character. If you do not use the-e option, it is output as-is:

Value of A is 10\n

The following escape characters can be used in Echo:

Escape Character	meaning
\\	Back slash
\a	Alarm, Bell
\b	BACKSPACE (delete key)
\f	Page Break (FF), moving the current position to the beginning of the next page
\ n	Line break
\ r	Enter
\ t	Horizontal tab (Tab key)
\v	Vertical tab

you can suppress escaping by using the-e option of the Echo command, which is not escaped by default, or by using the-N option to prevent the insertion of line breaks.

This article is from the Linux Security Advisor blog, so be sure to keep this source http://chengyangyang.blog.51cto.com/9473151/1700113

Shell substitution: Shell variable substitution, command substitution, escape character