After the user logs on to Linux, a system prompt symbol appears, which allows you to enter a lot of commands after the symbol and get the desired effect, who is behind the scenes who is helping us with this whole pile of things? is the shell, and when the user logs in, it actually goes into a program called the shell. The shell acts as a translator, translating each command entered by the user into instructions that the Linux system can recognize.
Interactive mode – when the shell receives a user input command, it starts executing the command and displays the results to the screen, and the shell displays the system prompt after the end, waiting for the user to enter the next command.
run in the background – the symbol for running in the background is "&", with the "&" symbol appended to the command, you can put the program in the background to run. – How does a program that executes in the background make it back to the foreground to run? Executes the FG command. – The program is already running in the foreground and can be placed in the background with CTRL + Z. – if more than one process is running in the background, execute the jobs command to list all the processes that are executing in the background, the number in brackets ([]) is the name of jobs, and the specified background process can be resumed by FG%number.
input and output redirection – Redirect standard input output through the redirect > "<".
Pipe – by pipe symbol "|" Completes the sequential processing of a series of commands.
Wildcard Character – The function of wildcards is to use wildcard characters to blur one or more character
environment variables when processing a file –shell is a huge program, in order to make the working environment conform to the user's custom or application needs, you can let the user set the shell environment.
shell Script –shell The most important and most responsible is the shell script. In addition to explaining commands, the shell has an important function of programming language, which can be programmed by the shell script process to accomplish more complex functions.
What is a shell?
