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How to Issue Commands in Linux
The Linux environment is interactive. When you type a command at the keyboard
and then press the Enter or Return key, Linux immediately begins
to act on the command. More accurately, Linux interprets the command using a
special program of its own called the shell. (On Milk Shake, the default
shell is bash.) All shells produce a shell prompt to let you know that Linux is
awaiting your next command. Milk Shake's shell prompt has the form username@host:~$,
where host is the name of the Linux system you are using (e.g.
andrew@milk:~$). Whenever you see this prompt, you know that
the Linux shell is ready for your next command.
Linux is case-sensitive. That is, Linux distinguishes between upper and
lower case letters in the names of files and programs. Thus, while ls is
a valid Linux command, LS is not. Login names and passwords are also
case-sensitive.
Some programs, such as Pico, have their own commands that you type within
the program rather than at the Linux shell prompt. However, the shell prompt
reappears whenever you exit such programs.
Basic File Commands
These are typed at the shell prompt username@host:~$.
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ls
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List the files in the current
directory
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ls -a
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List all the files in the current directory, even the
hidden ones
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ls -F
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As above, but indicate sub-directories by appending a
backslash (/) to their name
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cp FILE1 FILE2
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Make a copy of FILE1 and call the copy FILE2
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mv FILE1 FILE2
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Rename a file from old name FILE1 to new name FILE2
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mv FILE1 DIR/
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Move a file from it's present directory into another directory
(DIR)
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rm FILE
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Remove or delete FILE
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more FILE
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Display the contents of FILE, pausing after each screenful
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--More--(18%)
Whenever you see something like the above at the bottom of your screen, you
can:
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press the space bar
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To see the next screenful of text
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type b
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To go back one screenful
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type q
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To quit the listing of text and return to the Linux shell
prompt
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Correcting Typing Mistakes:
(at the Shell Prompt)
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Delete or Backspace
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Erase the last character you typed
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Ctrl -u
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Delete the last line you typed
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Basic Directory Commands
These are typed at the shell prompt username@host:~$
In Linux your files are organized in directories and subdirectories. When you first
log in to your account, you are placed in your home directory, which you can
refer to with the character ~.
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cd DIR
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Go to the directory called DIR
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cd ..
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Go to the directory above the current directory
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mkdir DIR
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Create a new directory called DIR
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rmdir DIR
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Remove the directory DIR (must be empty first; if not,
use rm -r)
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cd or cd ~
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Go to your home directory
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mv DIR1 DIR2
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Move or rename a directory from old name DIR1 to new name
DIR2
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Use the / character to
separate directory and file names when specifying a path.
Useful Commands
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exit
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Ends your work on the Linux system
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Ctrl-l or clear
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Clears the screen
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Ctrl-c
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Stops the program currently running
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Ctrl-p
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Retrieves the last shell command you typed
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Ctrl-z
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Pauses the currently running program
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man COMMAND
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Looks up the Linux command COMMAND in the online manual
pages
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find . -name FILE -print
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Finds all paths containing FILE in the current directory
or below it
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fgrep -i PATTERN FILE
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Searches for and displays all lines in file that contain
PATTERN (case insensitive)
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finger USER@ADDRESS
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Displays login/e-mail status of a user at another host
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jobs
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Lists background jobs started during your current login
session
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ps
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Lists all jobs (background and foreground) started during
your login session
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du
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Displays disk usage in kbytes by directory, starting in
the current directory and working down
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du -s
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Displays total disk usage
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fs listquota
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Displays your current disk space usage and quota in kbytes
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telnet ADDRESS
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Logs on to another machine on the Internet on which you
have an account
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ftp ADDRESS
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Begins a file transfer session with another computer on
the Internet
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wc FILE
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Counts the lines, words, and characters in FILE
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spell FILE
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Reports possible misspelled words in FILE
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Linux Shell Short Cuts
The Linux shell keeps a record of the commands you type during your login
session. Here are a few commands that take advantage of this history facility.
All are typed at the shell prompt username@host:~$.
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history
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List all commands typed so far (default maximum number=500)
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!!
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Repeat the last command
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!n
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Repeat command n from the history list
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!PATTERN
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Repeat last command beginning with PATTERN
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^PATTERN1^PATTERN2
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Repeat last command but replace PATTERN1 (usually a typo)
with PATTERN2 (the correction)
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