What is Command in Linux

By | 16/02/2014

 A command is an instruction given by a user telling a computer to do something, such a run a single program or a group of linked programs. Commands are generally issued by typing them in at the command line (i.e., the all-text display mode) and then pressing the ENTER key, which passes them to the shell.

An important feature of Unix-like operating systems is the large number of standard commands that are available, as well as the numerous options for many of them, as compared with other operating systems.

The shell is a program that takes your commands from the keyboard and gives them to the operating system to perform. In the old days, it was the only user interface available on a Unix computer. Nowadays, we have graphical user interfaces (GUIs) in addition to command line interfaces (CLIs) such as the shell.
On most Linux systems a program called bash (which stands for Bourne Again SHell, an enhanced version of the original Bourne shell program, sh, written by Steve Bourne) acts as the shell program. There are several additional shell programs available on a typical Linux system. These include: ksh, tcsh and zsh.
What is Command in Linux
A command consists of a command name usually followed by one or more strings (i.e., sequences of characters) that comprise options and arguments. Each of these strings is separated by white space (which consists of one or more spaces or tabs). The general syntax for commands is
command [options] [arguments]
The square brackets indicate that the enclosed items are optional. Most commands have at least a few options and can accept (or require) arguments. However, there are some commands that do not accept arguments, and a very few with no options.
The clear command, which is used to remove all previous commands and output from the display screen, is one of the rare commands that accepts neither options nor arguments. That is, it can only be used as follows:
clear
The shell is a program that takes your commands from the keyboard and gives them to the operating system to perform. In the old days, it was the only user interface available on a Unix computer. Nowadays, we have graphical user interfaces (GUIs) in addition to command line interfaces (CLIs) such as the shell.
  • A program that interprets commands
  • Allows a user to execute commands by typing them manually at a terminal, or automatically in programs called shell scripts.
  • A shell is not an operating system. It is a way to interface with the operating system and run commands.

What is Command in Linux

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