How Do I Become a Master Control Operator?

In order to request services (such as requesting IO or resource allocation) and responding to interruptions or errors, running programs must continuously reference various parts of the operating system. At a higher level, programs and files (including system programs and files) Instruction information and command information are operator control languages, also known as control languages or job control languages. System users use these languages to communicate instructions and requests for their jobs, resources, and files; machine operators use similar languages to control and query the allocation of hardware and software resources, and respond to system information and errors.

The interface between the system and the user actually provides a language for communication.

The UNIX operating system is a time-sharing multi-user, interactive software system. Its interface with the user is a command language, called the Shell language, and its interpreter is also called

In order to facilitate the interaction between the user and the relevant process, they often interact with the input and output parts of the terminal related to the process. But in some cases, for example, if the user has stored the necessary output information in a certain file in advance, or wants to get the output information in a certain file, then it is necessary to change the standard input and output files to match the specified file. Or devices are connected, SHELL provides a means for users to make the above requirements, which is called standard input and output steering.

1 Operator control language example 1

Simple command: cat file1 file2

Function: Display file1 and file2 in the standard output file in order.

But if you need to change the standard output, you can write: cat file1 file2> file3

Role: The standard output is turned to the ordinary file3.

Note: If the original file 3 does not exist, the SHELL interpretation library must first create it; if it already exists, it is considered to be a blank document, and it must be rewritten.

2 Operator control language example 2

cat file1 file2> / dev / tty03

Role: display for another terminal.

cat file1 file2> / dev / plp

Role: Turn to printer

3 Operator control language example 3

If you want the output to be added to the end of an existing file when you execute a command, you should use another output redirection ">>".

cat file1 file2 >> file3

The standard input characters can also be changed, for example: we <file, using file as the standard input when executing the shell command we. When this command is executed, the number of lines, words, and characters in the "file" file are sent to the standard. Output. ^[1]