Linux commands share a simple, common structure. This section describes their common structure and explains how you can obtain helpful information about the commands available to you.
The general form of a shell command line is this:
determines what operation the shell will perform and the
customize, or fine-tune, the operation.
The options and arguments
may or may not appear, as indicated by the square brackets. Sometimes
the command specifies a program file
that will be launched and run; such a command is called an
. Linux generally stores these files in
/usr/local/bin. System administration commands
are generally stored in
/usr/sbin, which are included by default in the
path of the root user. When a command specifies a program file, the
shell passes any specified arguments to the program, which scans and
interprets them, adjusting its operation accordingly.
Some commands are not external program files; instead they are
commands interpreted by the shell itself. One important way in which
shells differ is in the built-in commands that they support. Later in
this section, you’ll learn about some of
bash’s built-in commands.
The name of a Linux command almost always consists of lowercase letters and digits. Most commands let you specify options or arguments. However, in any given case, you may not need ...