As you read my tutorials on linux commands I am very sure you feel more confident with yourself while you see a console. I have explained many different things so far, from very basic built-in commands such as ls, cd, pwd, mv to more advanced ones such as pdfimages which helps to deal with images in pdf files.
But the learning never ends. I have been a linux user for more than four years now and I learn a new command every day. Knowing many commands does not only help you to perform different tasks through the console of your machine, but also helps to solve a problem in different ways.
Are you ready to learn some new more commands? If so then continue reading this article. There are so many things you need to learn in your way of becoming a linux ninja.
You might want to read our previous parts of this series.
- Some Basic Linux Commands I Have Used During My Linux Journey – Part 1
- Some Basic Linux Commands I Have Used During My Linux Journey – Part 2
- Some Basic Linux Commands I Have Used During My Linux Journey – Part 3
- Some Basic Linux Commands I Have Used During My Linux Journey – Part 4
- Some Basic Linux Commands I Have Used During My Linux Journey – Part 5
- Some Basic Linux Commands I Have Used During My Linux Journey – Part 6
The head command
As the name suggests the head command is used to output the first part of a file to standard output. According to the documentation it prints the first 10 lines of each file to standard output. When no file is specified it reads from standard input. But how to use this command on your console?
The basic usage is very simple. Open a new console on your machine and type the following command.
head filename_in_here
For example the following command displays the first 10 lines of my test.txt file on standard output.
head test.txt
The output of the above command is shown below.
this is 1 this is 2 this is 3 this is 4 this is 5 this is 6 this is 7 this is 8 this is 9 this is 10
The cmp command
The cmp command can be used to find the difference between two files. It shows the the offsets and line numbers where two files differ. To make it more practical for you guys while explaining this command I am using my favorite text editor to create the two following files shown below.
names.old names.new
Lets run the cat command which you have learned in previous series and see what each files contains.
cat names.old
The above command prints the following to standard output.
oltjano
Then running the following command will show a different output.
cat names.new
The output of the above command is shown below.
jetbird
As you can see from the results of cat command each one of the files contains only one single line of text. Now running the cmp command will show me the difference between the two files. You can easily tell it yourself, but what if you have files with million lines of text?
cmp names.new names.old
Running the above command gives the following standard output on my console.
names.new names.old differ: byte 1, line 1
As you can see from the output shown above the cmp command tells exactly where the two files differ. It shows the difference in a very clear way for the user to understand. In short words it tells the first byte and line number where they differ.
The hostname command
The hostname command can be used to show the system’s hostname. To use it just follow the very simple syntax which is shown in the example below.
hostname
Running the above command on my console gives me the following output.
baby
The logname command
The logname command prints the user’s login name. Run it as shown below.
logname
Running the above command on my console gives me the following output.
oltjano
The users command
If you would like to print the names of the users currently logged in then type the following command on your console.
users
The units command
The units command becomes very useful when you want to convert units from one scale to another. The units tool can be used interactively with prompts.
This tool does not come as a builtin on linux you have to install it . Ubuntu user can use the apt package manager to install it like shown below.
sudo apt-get install units
Once you have installed units on your machine run the following example.
units '2 kilometers' 'meters'
What output do you get? Is your output the same as mine?
* 2000 / 0.0005
The ping command
The ping command is used to test a network connection. It sends ICMP ECHO_REQUEST to network hosts. Use the following syntax to ping a host.
ping host_here
For example the following command is used to ping google.com
ping www.google.com
And the response of the ping is shown below.
PING www.google.com (74.125.29.104) 56(84) bytes of data. 64 bytes from qg-in-f104.1e100.net (74.125.29.104): icmp_req=1 ttl=42 time=346 ms 64 bytes from qg-in-f104.1e100.net (74.125.29.104): icmp_req=2 ttl=42 time=265 ms 64 bytes from qg-in-f104.1e100.net (74.125.29.104): icmp_req=3 ttl=42 time=289 ms 64 bytes from qg-in-f104.1e100.net (74.125.29.104): icmp_req=4 ttl=42 time=313 ms 64 bytes from qg-in-f104.1e100.net (74.125.29.104): icmp_req=5 ttl=42 time=336 ms 64 bytes from qg-in-f104.1e100.net (74.125.29.104): icmp_req=6 ttl=42 time=182 ms
Use CTRL+C to stop the ping.
The dirs command
The dirs command is used to display a list of remembered directories. Run it like shown in the following example.
dirs
The du command
The du command is used to estimate file space usage. Run the following command on your console and see what happens.
du
The kill command
The kill command is used to send a signal to a process. It is very useful when you want to kill a process that you no longer need. The signals listed below may be available for use with kill. When known constant, numbers and default behavior are shown.
Name Num Action Description 0 0 n/a exit code indicates if a signal may be sent ALRM 14 exit HUP 1 exit INT 2 exit KILL 9 exit cannot be blocked PIPE 13 exit POLL exit PROF exit TERM 15 exit USR1 exit USR2 exit VTALRM exit STKFLT exit might not be implemented PWR ignore might exit on some systems WINCH ignore CHLD ignore URG ignore TSTP stop might interact with the shell TTIN stop might interact with the shell
To kill a process use the following syntax.
kill PID
You can use as many PIDs as you want in a single command.
The following is an example of using the kill command.
kill 130
The above command is going to kill the process with the PID specified above. In my case it is not going to work as I do not have such a process running on my machine.
The following is displayed on my console when running the above command.
bash: kill: (130) - No such process
As you can see bash tells you that is no such process running on your machine. You can display a list of processes by using the following command.
ps aux
Then you can use piping to grep the process you want.
Or you can do the following.
ps aux | less
The locate command
The locate command is used to find files by name. This command prints matching files to standard output. According to the documentation in the manual pages locate reads one or more databases prepared by updatedb(8) and writes file names matching at least one of the PATTERNs to standard output, one per line.
locate test.txt
What should you know so far
Reading this series of linux commands has been a long process, but have you ever asked yourself what have you learned so far? In my opinion you should know the following:
- how to list files using the ls command
- how to navigate through directories using the cd command
- how to print the current working directory using the pwd command
- how to display the current date on your console
- how to copy files with the cp command
- how to remove files with the rm command
- how to kill a process with the kill command
- how to find information about your computer with the uname command
Conclusion
There are so many commands on your head right now and I know it sounds very hard for you to know how to use all of them. Many of you who are new to linux will feel very confused. I felt the same way when I started learning linux commands. But when I look back I see the progress I have done.
I am not a linux ninja, but I know how to do basic stuff. Keep learning.
