8.6 Pipe character and job control 8.7/8.8 shell variable 8.9 environment variable configuration file

8.6 Pipe symbol and job control
Pipe break: The data from the previous command to be output to the screen as the standard input of the latter command
Job Control: When you run a process, you can use CTRL + Z to pause it, then the FG (foreground) command resumes, or use the BG (Backgroung) command to make it run in the background (CTRL + C can also make it stop)
Use jobs to see the paused commands and numbers

8.7/8.8 Shell variables
Variable names can only consist of letters, numbers, underscores, and cannot start with a number, otherwise an error occurs.
When the contents of a variable are marked with a special symbol (such as a space): a single quotation mark must be added
The difference between single and double quotation marks:
Single quotes: What can be said to be WYSIWYG: the contents of a single quotation mark are output as-is, or are described as single quotes inside what will be output
Double quotation marks: The contents of the double quotation marks out, if there are commands, variables, etc., will first parse the variables, commands, and then output the final content to
Both Env and set can view variables
Export variable name = variable value sets the global variable, allowing all users in the system to use the variable after logging in. You can do this by adding the export Myname=aminglinux to the last line of the/etc/profile file and then running the Source/etc/profile (switching to another user can also take effect)





8.9 environment variable configuration file
/etc/profile User environment variable, interactive, (source/etc/profile) login to execute
/ETC/BASHRC users do not have to log in, the execution shell is effective

8.6 Pipe character and job control 8.7/8.8 shell variable 8.9 environment variable configuration file