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System utility commands.

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These are very basic commands that

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are being used in Linux environment.

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Some of those commands are just like, in Windows

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we have time, we have calendar.

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Now Windows is a GUI environment and you

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could view those time and calculators and stuff

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like that by going to the accessories.

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But in Linux it's not possible.

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So that's why there are commands that are

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being built that tells you to the date,

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the uptime information, the hostname, the uname,

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then about the operating system, which means where

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the commands are located, the calculators, sorry, the

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calendar and the bc is binary calculators.

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Now let's look at our Linux machine

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and run these commands one by one.

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In Linux machine when you are logged in through the

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GUI, through the console, you'll see the time here.

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You also have the option to go into

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the applications and pull up the calendar and

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you'll see all the information that are automatically

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viewed without running any command.

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But what if you are logging in

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through the PuTTY or the terminal client?

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And as I said before, 98% of the time you will be

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logging in through the PuTTY client to the terminal where you're not

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going to be able to see all those GUI environment.

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So let's look at the view through the

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PuTTY. Again, we'll put in our IP address.

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It's 192.168.56.101, and I remember by now and

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if you don't, you could just simply go back

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to your console and type ifconfig, enter.

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And at the top right here, this is the IP address.

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You punch in that IP address right

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here and click on Open Terminal.

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It will open up, you login as yourself.

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Put in the password and you are logged in.

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Once you clear the screen, and you will see here

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there is nothing but the black terminal. So when you wanted to run,

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when you wanted to find out what time

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is it or what date it is,

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you just type date.

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It will tell you today is Tuesday, March

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13, the time and the second and Eastern

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Daylight Saving time and the year.

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So that's what the date command is used for.

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It's very simple, and sometimes the date command

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is used to combine with the script.

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So a script will wake up, it checks

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the date, and it will run certain scripts,

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we'll cover that in our scripting session.

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The next one is uptime.

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uptime simply tells you how long been the system

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up for, and how many users have been logged

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into the system, and the load average.

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The next one, it tells us about the

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hostname, right here, the hostname.

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Let's move this little to the side. hostname,

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we could go back to our console, we could

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do the hostname, and you'll see this is

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the hostname of our Linux machine.

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And hostname is one of the important command

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that I would recommend you to run every

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time you log into the system,

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so you would know you are not logging

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into the wrong system, and you are not

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running very critical commands on the wrong system.

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You clear the screen.

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The next one we have uname.

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When you type uname, it will

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tell you it's a Linux machine.

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Again, in the Linux machine,

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you do need to run this command because sometimes

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in an environment you have Linux, you have Solaris,

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you have AIX, many different Unix flavors.

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So it's good to run uname.

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If you want to know more details about

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uname, you type uname -a.

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It will give you a lot more detail than just

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Linux. It will give you the hostname, the Kernel version,

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the time it was built, and other architecture information.

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The next command we need to learn is which. which command

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tells you the location of your command that you run.

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Let's say you run the command pwd, right?

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And it tells you that the command is

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telling you which directory you are in.

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So where is that command located?

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Of course, every command is a

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file itself, and it's located somewhere.

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To find out, you type which pwd, and it tells

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you this command pwd is located in /usr/bin/pwd.

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If you want to know more attributes about this command,

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you will run ls l-l /usr/bin/pwd, and you

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will see right here, this is the script

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actually, the command itself is a script.

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The script itself is a text file

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that has been written by developers.

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And it tells you right here it is owned

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by root, and the group is owned by root,

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and these are the permissions of this file.

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Everybody has the right to execute it.

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If I take this bit out, then I cannot

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run or nobody else can run this command.

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So this is what which command does.

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Let's clear this out.

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If you want to know where is date command located,

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date command is also located in /usr/bin/date.

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So, as you can see, most of

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the commands are located in /usr/bin.

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You do ls -l, and you

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see a whole bunch of commands.

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If you want to view one page at a time, you could

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do more, and you could see all these commands that we have.

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There are a bunch of commands that Linux has.

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What if I wanted to know how

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many total commands are in Linux? Very simple.

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You do ls -l and if you remember,

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you pipe it, you do wc -l.

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This would give me the total number

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of all these lines that are coming up.

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It's telling me there are 1597 commands

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that are inside of this Linux machine.

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Moving on.

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What if I wanted to know calendar?

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If I just type cal, it will give me

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the calendar of this month and this year.

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What if I wanted to know the month when I was born

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let's say? For training I'll do cal, September 18, 1977.

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So I'll type September 9, sorry September which is a

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month, 1977, and it would give me, I could look at it,

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September 18 was Sunday, so you could type any

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month followed by the calendar. If you just wanted

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to know all the months in the year 2016.

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So you just type cal 2016 and it'll give you

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all those months starting with January ending in December.

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That's what the cal command is used for.

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Next command we have, let's clear this,

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bc. bc stands for binary calculator.

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If you want to do the calculation, of course

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you could go in here and bring the calculator.

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But you don't want to bring the calculator

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GUI mode, you are in terminal mode.

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So you wanted to use the calculator.

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Then what you do, you type again bc, hit Enter.

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Now if you want to do two plus two, hit Enter.

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It will give you four.

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What if 256 times 321?

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That's the answer.

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So this is just a basic calculator.

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You could do division, multiplication,

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or anything that you want.

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If you want to quit out of it, just

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type quit, and you will be out of it.

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So these are a few system utility

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commands and you could run that.

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These are fun commands, come up with the different options,

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and of course to look at the options,

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you could do man on every

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command and run with few options.

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[No audio]