Shell script knowledge point 1 (continuously changing Series 3)

It has been a while before the first post has been changing the series. At that time, I was just in touch with shell scripts and will be used temporarily at work. Learn the same thing, love the same, step by step.

1. Single and Double quotation marks

Single quotes tell shell to ignore all special characters, while double quotes only need to ignore the majority. Specifically, three special characters enclosed in double quotes are not ignored: $ ,\,', double quotation marks explain the special meaning of strings, while single quotation marks directly use strings.

2. Differences between running scripts using SH,./And Source:

If a non-built-in script such as a sub-shell exists in the former script, a sub-shell environment will be created, and the latter will not.

3. Compiled and interpreted languages

Compiled languages: C ++, Java, and C

Interpreted language: shell, Perl

4. Global and local variables in Shell

Global variables can be declared through the configuration file, or export.

A variable in a method cannot be a local variable. It is valid if it changes a variable with the same external name.

Local variables must be declared