Linux execution script specification and execution commands

1. Specify the script interpreter at the beginning

#!/bin/bash or #!/bin/sh

2, and then add version information, etc.

#Date: 2016-12-27

#Author: sadoc.blog.51cto.com

#Mail: [Email protected]

#Function: Scripting Features

#Version: Version

The script is named after the. sh extension

"source" and " . "Load the executed script, the variable (including function) value in the script after the end of the script still exists in the current shell,"sh" and" bash "is not

Global variables:/etc/profile variables under this directory all users are in effect

Current User variables:. bash_profile variables are only valid in the current user mode

Export variables with export

Modifying a Set Variable environment requires "." The "source" load takes effect

For example: Vim /etc/profile or . Bash_profile added

Export A=nihao

The difference between a single quote, a double quote, and a non-quoted variable:

Single quotes:

That is, the single quote content is output as is, or what you see in single quotation marks.

Double quotes:

If there are commands and variables inside the double quotes, the variables and commands are parsed out and then the final content is output.

No quotation marks:

Output of the content, the string containing the space will be treated as a whole output, if there is a command or variable, will be the command variable parsing output, if the string with a holding and other special characters, it is not fully output, need to use double quotation marks.

Linux execution script specification and execution commands