Linux Command Line Structure

Linux Command Line Structure

A command in Linux is a program that instructs the system to perform a specific task. The general structure of a command is:

• command [options] [arguments] 

► Arguments: These indicate what the command should act upon, often a file or a set of files.

► Options: These modify how the command is executed

Commands are case-sensitive, so "command" and "Command" are different.

Using Options

Options are generally preceded by a dash (-). It is possible to combine multiple options together:

• command -[option][option][option]

For example, the following command displays a detailed list of files in the current directory and all its subdirectories:

• ls -alR

For example, the following command displays a detailed list of files in the current directory and all its subdirectories:

• ls -alR

► -a : shows all files, including hidden files.

► -l : detailed display mode.

► -R : recursion into subdirectories.

Separating Options

It is also possible to separate the options with spaces, placing a dash before each one

• ls -a -l -R

Options with Parameters

Some options require parameters. For example, to send two copies of a file to a specific printer 

• lpr -Pprinter3 -#2 file

This sends 2 copies of the file to the printer named printer3.

Exceptions

It is important to note that not all commands strictly follow these conventions. Some may not require a dash before options, and others may not allow options to be grouped.

To learn more about specific options for a command, simply consult the manual page for that command using:

• man command