Linux Shell - Love is Forever

Linux Shell
Linux Command-Line Interface
■ Linux shells: A shell is a command interpreter
that allows you to type commands from the
keyboard to interact with the operating system
■ sh (Bourne Shell) The sh shell was the earliest
shell, being developed for UNIX back in the late
■ bash (Bourne-Again Shell) The bash shell is an
improved version of the sh shell and is one of the
most popular shells today. It’s the default shell
used by most Linux distributions.
■ csh (C Shell) The csh shell was originally
developed for BSD UNIX. It uses a syntax that is
very similar to C programming.
■ tsch The tsch shell is an improved version of the
C Shell. It is the default shell used on FreeBSD
■ zsh (Z Shell) The Z Shell is an improved version
of the bash shell.
Linux Command-Line Interface
• Libraries Libraries are pre-written code
“pieces” that application programmers use
in their programs.
• Utilities maintaining the file system,
editing text files, managing running
processes, and installing new software
• User Interface command-line interface
(CLI) and a graphical user interface (GUI).
Linux Command-Line Interface..
Commonly Used CLI Commands
and Utilities
/ : denote root directory
./ : denote current directory
■ halt This command shuts down the
operating system, but can only be run by
the root user.
■ reboot This command shuts down and
restarts the operating system. It also can
only be run by root.
Commonly Used CLI
• man: is help command. Ex: man ls
– Press q to quit
– /xyz to search string in man page
• pwd: Display current Directory
cd: Changing Directories
# go to home directory
cd ~/papers # go to /home/user/papers
cd ~fred
# go to /home/fred
cd dir
# go to directory (relative)
cd /dir1/dir2/dir3...
# go to directory
• cd # go to last directory you were in
cp: copy file
• cp file1 file2 # copy file1 to file2
• cp file1 directory # copy file1 into
• cp file1 file2 file3 ... directory # copy files
into directory
• cp -R dir1 dir2/
# copy dir1 into dir2
including subdirectries
Commonly Used CLI Commands
• date - Shows current date
date Sat Aug 31 17:18:53 BST 2002
logout - Closes the current shell. Also try
rm - Delete (remove) files
• rm file1
# delete a file (use -i to ask
whether sure)
• rm -r dir1
# delete a directory and
everything in it (CARE!)
• rm -rf dir1 # like above, but don't ask if
we have a -i alias
■ su (switch user) This command switches
the current user to a new user account.
This command is most frequently used to
switch to the superuser root account. In
fact, if you don’t supply a username, this
utility assumes that you want to change to
the root account. If you enter su -, then
you will switch to the root user account
and have all of root’s environment
variables applied.
■ env This command displays the
environment variables for the currently
logged-in user.
■ echo This command is used to echo a
line of text on the screen. It’s frequently
used to display environment variables.
Ex: echo $PATH
■ top This command is a very useful
command that displays a list of all
applications and processes currently
running on the system.
■ which This command is used to display
the full path to a shell command or utility.
Ex: which ls
It display: /bin/ls
■ whoami This command displays the username
of the currently logged-in user.
■ netstat This command displays the status of the
network, including current connections, routing
tables, etc.
■ route This command is used to view or
manipulate the system’s routing table.
■ ifconfig This command is used to manage
network boards installed in the system. It can be
used to display or modify your network board
configuration parameters.
Linux Graphical User Interface
• XFree86 project developed a free
windows system that provides a GUI on
the Linux operating system. Using X
Windows along with a window manager
and a desktop environment (such as
GNOME or KDE), users can interact with
the Linux kernel using a mouse instead of
the keyboard.
• GNU –
• Question 13?

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