Command line Mini Howto for linux. (I am using ubuntu 7.04 and kde 3.5.6)               Back to Main Page          

This i a very short version, and if you want to know more, go to the Internet etc.                                    

This howto is without any guarantee, and you may use it on your own responsibility only.

There may be errors, but I do not want to use too much time to  write this howto.

My idea is to make documentation, so you can at least start using the system.

I (66 years old) have abstracted what I find most important, from lots and lots of documentation.

To check specific words you may  click here to open wikipedia  (use search box, left side middle).

It's easiest to print this howto out, to use it, by your side !


Index:

Open a Konsole - the command line

apropos - to find a man page

The Bash shell

Cat: To concatenate (join) files - or view contents of a text file

cd: Change working directory

chmod: To change file permissions

chown: Change file owner and group

cp: Copy a file

df: sizes of your mounted partitions

dmesg: to print out the bootup messages

mogrify: convert image files

locate: to find a certain file

ln: To make links between files

ls: Lists directory contents

mkdir: Make a directory
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mount: To mount a filesystem

mv: Rename file

ps:  Report a snapshot of the current processes (to see which programs are running)

pwd: Present working directory

rm: Remove files

rmdir: Remove empty directory

split: Splits a file into pieces

sudo: Execute a command as "superuser"

tar: The tar archive command

top: Display Linux tasks (to see which programs are running -and their PID's (Process ID)

whereis: locate the binary (file to start a program)




In order to use the command line open a Konsole.

Choose K-menu - System - Konsole:                                                                                                                                                    Back to Index



There are other Terminal programs to use (Terminal, xterm, yakuake etc.).                                                                                Back to Index

Below is shown how the Konsole looks with the "ls" command inserted on the command line, and the result of this command is also shown:



Bash is the default shell program used in most Linux distributions, e.g. Debian and Ubuntu etc.

For each Bash command, and a lot other linux commands, you can also give the "man" command followed by the very command name, like "man ls" for the "ls"

command, in order to see the documentation for the "ls" command - all man pages are organized in the same way.

You could take a quick look at: "man bash" and "man man".

Click here to get an alphabetically list of linux commands

I will following give a short explanation of some of the linux commands I use most:                                                                                Back to Index


apropos: Search in the "man" pages "Names" and "Description" sections for a keyword - see "man apropos".

Example: "apropos ls"


bash: Gives an explanation of the Bash shell - see "man bash"

Example: "man bash"


cat: To see content of a text file, or to concatenate (join together) files - see "man cat"

Example 1: "cat file.txt | less" - will show you the contents on the screen of the text file "file.txt" (one page at a time - shift page with the "Page Down/Page Up" button).

Example 2: If you have a lot of text files you want joined together to one big text file:

First copy all the files to an empty directory.

Then cd to that directory.

Then run: "cat * > bigfile.txt" - and all the files will be joined together into one file by the name "bigfile.txt".

Sometimes you might download a video file, split up into several files, called something like file.avi.000, file.avi.001 .... file.avi.98 etc. from a newsgroup server -

in this case copy all the files into an empty directory and run: "cat * > file.avi", and you have a complete video file called "file.avi" ready to play.
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cd: Change working directory

Example: cd /home/user4/howto - will bring you to the "/home/user4/howto" directory

pwd: Present working directory - see "man pwd" - will show you where you are:





chmod: To change file permissions - see "man chmod"

Example: "sudo chmod -R 644 /home" - change the permissions of the "/home" directory and all its subdirectories -and files to "rw-r--r--"

Example 2: "sudo chmod -R 777 /home" - change the permissions of the "/home" directory and all its subdirectories -and files to "rwxrwxrwx"

The permissions - r=read, w=write, x=execute - the letters are:   "rwx rwx rwx" - the equivalent numbers are:   "421 421 421"

Explanation:

"6" means "4+2+0" equals "rw" - "4" means "4+0+0" equals "r" - "4" means "4+0+0" equals "r" - result = "644"  equals "rw- r-- r--"

"7" means "4+2+1" equals "rwx" - "7" means "4+2+1" equals "rwx" - "7" means "4+2+1" equals "7" - result = "777" equals "rwx rwx rwx"

 
chown: Change file owner and group - see "man chown"

example: "sudo chown -R root:root /home" - Changes the ownership to user="root", group="root" for the "/home" directory with all subdirectories -and folders.


cp: Copy a file - see "man cp"

Example: "cp file.txt /home/user/a_directory/file2.txt" - This will copy the file "file.txt" from the directory where you are, to into the directory "/home/user/a_directory" and

give it the name "file2.txt"

cp: Copy several files with same extension ".txt"                                                                                                                    Back to Index

Example: cp *.txt /home/user/a_directory - This will copy all files with the extension ".txt" (like file1.txt, file2.txt and file3.txt) from the directory you are in, into the

directory "/home/user/a_directroy", and the files will keep their names in the new directory "a_directory".


df: Will show you the sizes of your mounted partitions - see "man df"

Example: "df -h" shows you the mounted partitions, their names -and sizes in a human readable size (the "-h" option):



Above you can see following:                                                                                                                                                        Back to Index

Partition "/dev/sda3" - size of 28 GB - mounted on "/" (Kubuntu on my system)

Partition "/dev/sda1" - size of 37 GB - mounted on "/media/sda1" (Ubuntu on my system)

Partition "/dev/sdc1" - size of 294 GB - mounted on "/media/disk" (An external harddisk on my system)

The rest of the output is a little more complicated to an average linux newbie.

As you can see, I have both Kubuntu -and Ubuntu installed on my harddisk.


dmesg: Helps users to print out their bootup messages - see "man dmesg"

Example: "dmesg | less" - Prints the output of the bootup messages to the screen, one page at a time (shift page with the "Page Down/Page Up" buttons).

Example 2: "dmesg > boot.messages" - Prints the output to a file "boot.messages" in the directory where you are.


mogrify: Can convert image files - see "man mogrify" - (is part of the "Imagemagick" package).

Example: mogrify -resize 50%x50% *.jpg - will convert all the jpg images in the directory where you are, into a smaller size 50% x 50%, and overwrite the images.

mogrify can do a lot more.


locate: To quickly search through all files on your system, to find a certain file - see "man locate"                                    Back to Index

In order to use this command, you must first update the locate database, by issuing following command: "sudo updatedb" - then wait some minutes.

Example: "locate fstab | less" - to find where the "fstab" file is located - it can sometimes give many suggestions, so you have go through the listed suggestions.

Note, that all suggestions are given with full pathnames to the file, like "/etc/fstab" etc.


ln: To make links between files - see "man ln". (A link is a small file, leading to a real file, when clicked).

Example: "ln -s real_file link_file" (The "real_file" is the real file [placed first], and the "link_file" is the link [which is placed last] ).


ls: Lists directory contents, lists both subdirectory -and  file names of a directory - see "man ls".

Example: "ls" - lists the contenst of the directory you are in.

Example 2: "ls -al" - lists the contents of the directory you are in, with more information.

Example 3: "ls -al | less - lists the contents of the directory you are in, one page at a time (use "Page Down/Page Up" to move down/up one page at a time).

Example 4: "ls -al /home/user" - lists the contents of the "/home/user" directory.


mkdir: Make a directory - see "man mkdir"

Example: "mkdir /home/user/another_directory" - creates a new empty directory of the name "another_directory" in the "/home/user" directory.


mount: To mount a filesystem (e.g. an external harddisk formatted with an ext3 file system) - see "man mount"                Back to Index

Example: "sudo mount /dev/sdc1 /media/disk" - means mount the external harddisk "/dev/sdc1" on the "/media/disk" directory - (this is normally done automatic).


mv: Renames files - see "man mv"

Example: "mv file.txt file2.txt" - renames the file "file.txt" to "file2.txt".


ps:  Report a snapshot of the current processes (programs) - see "man ps"

Example: "ps -A | grep firefox" - to find the PID (process ID) number of "Firefox"

To find the PID of "Firefox", and then to "kill" the program (thought situation, where the "Firefox" program has stopped working and we want to "kill" it (below):





rm: Remove files - see "man rm"

Example: "rm file.txt" - removes the file "file.txt" from the directory you are in.

Example 2: "rm *.txt" - removes all the files with the ".txt" extension from the directory you are in.

Example 3: "rm /home/user/*.txt" - removes all the files with the extension ".txt" from the "/home/user" directory.                        Back to Index


rmdir: Removes empty directories - see "man rmdir"

Example: "rmdir /home/user/a_directory" - removes the "a_directory" directory, which must be empty.


split: Splits a file into pieces - see "man split"

Example: split -b 20k bigfile smallfile - splits the big file "bigfile" into small files ("smallfileaa", "smallfileab", "smallfileac" etc) of 20 kb each.

To concatenate (join) the small  files into one big file, put all the small files into an empty directory.

cd to that directory.

Then run from the command line: "cat smallfile* bigfile", and the files are again joined into one big file "bigfile".


sudo: Execute a command as "superuser" - see "man sudo" (The superuser can execute commands, which a normal user cannot do - a safety measure).

Example: "sudo konqueror" - opens the konqueror webbrowser as superuser, which allows you to copy, move or edit files etc., owned by user "root".

When you exexute a sudo command you must insert your user password, when asked for it.


tar: The tar command, used to archive (create and compress) a big file from several directories and files, or unarchive (extract and uncompress) the

contents of a tar file  - see "man tar".                                                                                                                                            Back to Index

Example 1 (to create a tar archive):

Place all the directories and files you want to make into an archive file, into an empty directory.

cd into that directory.

Then execute: "tar cvzf archive.tgz *" - and the whole contents of the directory you are in is archived and compressed into the archive file "archive.tgz", and this file is

placed in the same directory.

Example 2 (to extract a tar archive):

Place the archive file "archive.tgz"  in an empty directory. (Please note: The ".tgz" extension is the same as the ".tar.gz extension").

cd into that directory.

Then execute: "tar zxvf archive.tgz" - which unpacks -and uncompresses the archive file "archive.tgz" into the directory you are in.


top: Display Linux tasks - see "man top"

Example: "top" - starts the top program, and you can see which programs are running, how much processor power they use (%) and their "PID's" and more.



whereis: locate the binary (file to start a program) - see "man whereis"

Example: "whereis gimp" - will give the path to the file "gimp" that starts gimp: "/usr/bin/gimp"

Note: Most binaries are placed in: /usr/local/sbin - /usr/local/bin - /usr/sbin - /usr/bin - /sbin - /bin

Most programs can be started from the command line, by just inserting its name (gimp, firefox, kate, kmail etc.) and then press "enter".

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9/2007