Now that we know that processes run, how can we go about finding processes?  There must be some way to find a particular process… like if I want to find every process that has the letter a in the name. Or if I want to find every process that has a name like ‘insight’ because I’m sure Hydra is running something on my system and I want to know what it is.  Or if I want to know every process that’s being run by a user with the name hydra.

You get the idea.  I want to find processes!

To do this, we’re going to combine two commands.  The first is ps, that useful command that lists the processes.  The second is that useful command grep that we used to find things in files.

ps auxw shows you every single process that’s currently running on a system.  On a system that’s very very busy, this can be a lot.  There’s 65536 processes allowed at any time, so combing through those looking for hydra (or Hydra or hYdRa) would take too long.  I’m lazy!  I want the system to do it for me!

From this post we know that grep has an option where it ignores case.  This means it can find hydra, Hydra, HYdra, HyDrA, or… I’m stopping that now.  It means you can find any combination of the 5 letters hydra no matter what capitals you use.

Now that we have those two commands, we’re going to combine them.  Remember this post on pipes?  We can take the output from one command, ps and pipe it through to the other command, grep.

Alpha:~ computerlamp$ ps auwx | grep -i hydra

Nothing was found from that command.  Hurray!  No Hydra user on the system!

…unless they’re hiding themselves.  Alexander Pierce didn’t have a username of Hydra.  He was hiding and probably had a user name of apierce or alexander or alexander.pierce or even supersecretary.  But not something we could actually look for in ps.

Remember ps a from this post? It showed what processes you were running in a single terminal.  If you want to see every single process you were running, no matter what terminal, then this combination of ps and grep  would work for you!

Alpha:~ computerlamp$ ps auwx | grep -i computerlamp

Finding processes is easy with that combination of ps and grep!

In honor of New Year’s Day, today we’re going to talk about more silly commands.

The first one is called yes

Alpha:~ computerlamp$ yes
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y
y

And it keeps going and going and going! It’s the Energizer Bunny of commands!

To stop it, hit control-C.  That’ll stop the Bunny, er, Y from streaming on your terminal.

So what’s this command for? Other than to fill your screen up with more y’s than should be legal. Well, remember from this post the xargs command? Some commands insist you sit there and type y over and over and over before they’ll finish. This command lets you do:

Alpha:~ computerlamp$ yes | xargs annoying_command

So you can be lazy and not type it over and over and… did I mention over? Then when that command finishes, your yes command will exit.

Linux® has lots of silly commands.  Another one has no redeeming feature at all. Aside from pure amusement. It’s called fortune.

Alpha:~ computerlamp$ fortune
Long life is in store for you.
Alpha:~ computerlamp$ fortune
Q:    What do you say to a New Yorker with a job?
A:    Big Mac, fries and a Coke, please!
Alpha:~ computerlamp$ fortune
So she went into the garden to cut a cabbage leaf to make an apple pie;
and at the same time a great she-bear, coming up the street pops its head
into the shop. "What! no soap?" So he died, and she very imprudently
married the barber; and there were present the Picninnies, and the Grand
Panjandrum himself, with the little round button at top, and they all
fell to playing the game of catch as catch can, till the gunpowder ran
out at the heels of their boots.
        -- Samuel Foote
Alpha:~ computerlamp$ fortune
You may worry about your hair-do today, but tomorrow much peanut butter will
be sold.

It even has a man page. You can type man fortune and see the flags it has too.

For example, if you only want short fortunes, then you could do:

Alpha:~ computerlamp$  fortune -s
How apt the poor are to be proud.
		-- William Shakespeare, "Twelfth-Night"

If you’re only interested in long fortunes, then you would do:

Alpha:~ computerlamp$  fortune -l
At once it struck me what quality went to form a man of achievement,
especially in literature, and which Shakespeare possessed so enormously
-- I mean negative capability, that is, when a man is capable of being
in uncertainties, mysteries, doubts, without any irritable reaching
after fact and reason.
		-- John Keats

The fortune command pulls it’s sayings from many different files. If you want to know what file the fortune came from, you would do:

Alpha:~ computerlamp$  fortune -c
(riddles)
%
Q:	How do you play religious roulette?
A:	You stand around in a circle and blaspheme and see who gets
	struck by lightning first.

As you can see, not all of the fortunes are polite.

So there you have it. Two silly commands found in Linux®.

Last post we introduced ps, this post we’ll talk about ps and flags. So, brief recap:

Alpha:~ computerlamp$ ps
  PID TTY          TIME CMD
17245 pts/2    00:00:00 bash
17248 pts/2    00:00:00 ps

Tada! ps with no flags.

Let’s start with a simple flag, x. In the first example, we saw every command that has a tty, or a direct connection to a terminal. That’s the default action of ps. What if we want to see every thing even if it doesn’t have a terminal?

Alpha:~ computerlamp$ ps x
12779 pts/2    R+     0:00 ps x
17245 pts/2    Ss     0:00 -bash

Well, that isn’t any different from the first time around, except now I see that I ran ps with a flag.

But wait, something is weird here. Since we started talking about flags, they’ve always started with a – aka a dash or a hyphen. That time, I didn’t use one. ps is an interesting command, it has three kinds of flags you can use. From the man page:

      This version of ps accepts several kinds of options:
       1   UNIX options, which may be grouped and must be preceded by a dash.
       2   BSD options, which may be grouped and must not be used with a dash.
       3   GNU long options, which are preceded by two dashes.

This means that there are flags that begin with a dash, flag that don’t begin with a dash and flags that have two dashes. If you use the kind without a dash then you can’t use the kind with a dash. It also means that ps -a and ps a are two different commands. See?

Alpha:~ computerlamp$ ps -a
  PID TTY          TIME CMD
12825 pts/2    00:00:00 ps
Alpha:~ computerlamp$ ps a
  PID TTY      STAT   TIME COMMAND
12832 pts/2    R+     0:00 ps a
13451 pts/2    Ss     0:00 -bash

And isn’t that confusing? It feels like Dr. Strange wandered in and the world went weird.

Next post, we’ll talk about processes again.  Understanding processes is key to understanding ps.

In one of my first posts I talked about this thing called a process. It happens when you run any program on a Linux® system, you create a process. If these things are running, how do I see them? Well, Linux&reg keeps them a table called a process table. We can see them with the command ps. You run it like:

Alpha:~ computerlamp$ ps

The output is kind of boring. It looks like:

  PID TTY          TIME CMD
17245 pts/2    00:00:00 bash
17248 pts/2    00:00:00 ps

It is just the processes that I’m currently running. bash is a shell and that is a program that gives me my command lines. We’ve been using it all along. There’s many kinds of shells, bash is one of the most common. It stands for Bourne Again Shell and was called that because it was a written as a replacement for a Bourne Shell. Wikipedia says it was first released in 1989. It’s been around a long time and it’s the standard command line interface on most Linux® systems.

The second command is the ps that we ran to get that command. If we had used any flags with ps, we would see those too.

The first column is the process id. Remember, Linux® understands numbers better than strings, so every process gets a number. It uses that id to refer to the process.

The second column is the tty. That stands for teletypewriter, a very very old device. According to Wikipedia it’s a typewriter that can be used to send messages to another typewriter. How’s that for very old school? Linux® took that history and made a tty mean terminal or output device. It’s the output device that that command is hooked up to.

ps is a command with many flags. Many MANY flags. We’ll talk about those in more posts.