Display a brief help on a command (works with most commands). "--help" works similar to DOS "/h" switch. The "more" pipe is needed if the output is longer than one screen.
• man topic
Display the contents of the system manual pages (help)
on the topic. Try man man first. Press "q" to quit the viewer. The command
info topic works similar and may contain more up-to-date information. Manual
pages can be hard to read. Try any_command --help for short, easy to digest
help on a command. If more info needed, have a look to the directory /usr/doc.
To display manual page from a specific section, I may use something like
in this example: man 3 exit (this displays an info on the command
exit from section 3 of the manual pages).
• apropos topic
Give me the list of the commands that have something
to to do with my topic.
• help command
Display brief info on a bash (shell) build-in command.
• ls
List the content of the current directory. Under Linux,
the command "dir" is an alias to ls. Many users have "ls" to be an alias
to "ls --color".
• ls -al |more
List the content of the current directory, all files
(also those starting with a dot), and in a long form. Pipe the output through
the "more" command, so that the display pauses after each screenful.
• cd directory
Change directory. Using "cd" without the directory name
will take you to your home directory. "cd -" will take you to your previous
directory and is a convenient way to toggle between two directories. "cd
.." will take you one directory up.
• cp source destination
Copy files. E.g., cp /home/stan/existing_file_name .
will copy a file to my current working directory. Use the "-r" option (for
recursive) to copy the contents of whole directories, e.g. , cp -r my_existing/dir/
~ will copy a subdirectory under my current working directory to
my home directory.
• mcopy source destination
Copy a file from/to a DOS filesystem (no mounting necessary).
E.g., mcopy a:\autoexec.bat ~/junk . See man mtools for related commands:
mdir, mcd, mren, mmove, mdel, mmd, mrd, mformat ....
• mv source destination
Move or rename files. The same command is used for moving
and renaming files and directories.
• ln source destination
Create a hard link called destination to the file called
source. The link appears as a copy of the original files, but in reality
only one copy of the file is kept, just two (or more) directory entries
point to it. Any changes the file are automatically visible throughout.
When one directory entry is removed, the other(s) stay(s) intact. The limitation
of the hard links are: the files have to be on the same filesystem, hard
links to directories or special files are impossible.
• ln -s source destination
Create a symbolic (soft) link called "destination" to
the file called "source". The symbolic link just specifies a path where
to look for the file. In contradistinction to hard links, the source and
destination don't not have to tbe on the same filesystem. In comparison
to hard links, the drawback of symbolic links are: if the original file
is removed, the link is "broken", symbolic links can also create circular
references (like circular references in spreadsheets or databases, e.g.,
"a" points to "b" and "b" points back to "a").
• rm files
Remove (delete) files. You must own the file in order
to be able to remove it. On many systems, you will be asked or confirmation
of deleation, if you don't want this, use the "-f" (=force) option, e.g.,
rm -f * will remove all files in my current working directory, no
questions asked.
• mkdir directory
Make a new directory.
• rmdir directory
Remove an empty directory.
• rm -r files
(recursive remove) Remove files, directories, and their
subdirectories. Careful with this command as root--you can easily remove
all files on the system with such a command executed on the top of your
directory tree, and there is no undelete in Linux (yet). But if you really
wanted to do it (reconsider), here is how (as root): rm -rf /*
• cat filename | more
View the content of a text file called "filename", one
page a time. The "|" is the "pipe" symbol (on many American keyboards it
shares the key with "\") The pipe makes the output stop after each screenful.
For long files, it is sometimes convenient to use the commands head and
tail that display just the beginning and the end of the file. If you happened
to use "cat" a binary file and your terminal displays funny characters
afterwards, you can restore it with the command "reset".
• less filename
Scroll through a content of a text file. Press q when
done. "Less" is roughly equivalent to "more" , the command you know from
DOS, although very often "less" is more convenient than "more".
• pico filename
Edit a text file using the simple and standard text editor
called pico.
• pico -w filename
Edit a text file, while disabling the long line wrap.
Handy for editing configuration files, e.g. /etc/fstab.
• find / -name "filename"
Find the file called "filename" on your filesystem starting
the search from the root directory "/". The "filename" may contain wildcards
(*,?).
• locate filename
Find the file name of which contains the string "filename".
Easier and faster than the previous command but depends on a database that
normally rebuilds at night.
• ./program_name
Run an executable in the current directory, which is
not on your PATH.
• touch filename
Change the date/time stamp of the file filename to the
current time. Create an empty file if the file does not exist.
• xinit
Start a barebone X-windows server (without a windows
manager).
• startx
Start an X-windows server and the default windows manager.
Works like typing "win" under DOS with Win3.1
• startx -- :1
Start another X-windows session on the display 1 (the
default is opened on display 0). You can have several GUI terminals running
concurrently. Switch between them using <Ctrl><Alt><F7>, <Ctrl><Alt><F8>,
etc.
• xterm
(in X terminal) Run a simple X-windows terminal.
Typing exit will close it. There are other, more advanced "virtual"
terminals for X-windows. I like the popular ones: konsole and kvt (both
come with kde) and gnome-terminal (comes with gnome). If you need
something really fancy-looking, try Eterm.
• xboing
(in X terminal). Very nice, old-fashioned game. Many
small games/programs are probably installed on your system. I also like
xboard (chess).
• shutdown -h now
(as root) Shut down the system to a halt. Mostly used
for a remote shutdown. Use <Ctrl><Alt><Del> for a shutdown at
the console (which can be done by any user).
• halt
reboot
(as root, two commands) Halt or reboot the machine. Used
for remote shutdown, simpler to type than the previous command.
