Unit 02 - Using Linux

28. Named Pipes

You have to remember that the man pages were designed to provide a manual of help to everybody, from beginners to experienced users, all the way through administrators, programmers, and anybody who, just like me, can't remember every single command that's out there. Having that is important. There's also what we call info pages, which are designed to give you the same kind of help for the end users. Now, man pages, we said, were help suitable for experienced users and programmers, and then we said, we have info pages for end users. It sounds like an insult. I hate to say it, but that is one of the things that we do insult people about. It seems like in the Linux environment,oh, they're just an end user, so they have special pages just for them. I know it sounds bad, but at some point, all of us were end users. Still, take a look at it. Don't feel bad if you look at an info page as though you're some newbie or noob, as we might say. Anyway, you've got this ability to get help, and I suggest you use it because it's right there, right in your shell. You type the command and you've got it. You don't have to go down to a bookstore, order a book, you don't have to search online only if those pages were not helpful enough for you or in the likelihood that you don't have a manual page for a certain thing you're looking up. Not all commands, not all features have a manual that you need to know as well.

29. Demo - Exploring Named Pipes

Alright, so we're going to do a little bit of some help commands and we're going to explore the manual. Now that I've moved to my gnome environment, I thought it would be kind of a nice little switch and we're going to do a couple of commands to remind us what we did,like the LS help so we can see the help files. Now I'm going to kind of do what we call a little bit of calling back. Just remember some of the other things we've talked about. Now when I type this in, you can see that this gave me way too much information that I can see on one screen and I either have to scrollup or find another way to deal with that. So let me clear and remember that piping was taking the input of one command and sending it to a new command. In this case, the more command, now you can see that it breaks it down and lets me read it page by page. If I hit the spacebar, I'm going to go ahead and type a whole page. If I hit the Enter key whenever you see more spacebar, it moves a page. Enter moves a single line. When you're done, you can type in Q or Controlc. That was a queue to be able to stop it. All right, so I'm going to clear that screen again. Let's take a look at the manual. Now I'm going to do the manual for LS. Now the manual is broken down into different sections and you can see the names of like the first section. It's got a name, synopsis, and description. Now down at the bottom here you see a little colon and that little colon is just kind of waiting for some extra commands and I'm not going to necessarily take you on that tour just yet, but I'm just going to hit thespacebar to keep going page by page. But if I type anything other than the letter Q, it's actually going to try to help me look through as a research tool to find a certain set of words. But again, I'm just going to hit the letter Q and it will let me quit. So again, you are going to experiment, I hope, and play with some of these options a bit on your own. Now I'm going to try and man two LS and we'll see if section two even exists in that manual and it doesn't. In fact, the only one we saw was section one, manone LS, and that's what it's telling me up here that it was section one and that's all we saw. But remember that there are potentially several sections in each manual, and it might be of help for you to look for them. Let's try the main locale. And now here I'm taking a look at the different types of information, hit the spacebar and it pretty much took me through to the end, it looks like quite quickly. So hit the queue. Let's try man seven of the locale for that command. And again, no particular entry. So it's just a matter of knowing the entries and knowing what you're wanting to find. And I'd have to say that you want to work with the man in command to figure out how it's going to be of help. But generally speaking, I don't think you have to worry about the sections. Man by itself opens up the manual of almost every command. And the locale is another example of an acommand that is not on every system. By the way, this is a part of the Pro Programmers' Reference Guide. But again, it's just as a way of helping you understand a little bit more about each command. It gives you help without having to download a CD or go to the Internet. And that's what the manual does.

30. Getting Help

Alright, so now there are other helpoptions that are available to you, especially for what I call this "Catch 22." Let's say you know, there's a command that does something,but you can't remember the name of the command. Then that means you can't type in the manual command to figure out what the command does because you don't know another name for the command. You can see the tough predicament. So there are two searches that you can do to help you find the manual pages that would deal with a particular command, so long as you know kind of what it did. In other words, if you knew there was something that sent the output to a text file, you could put in a command called Mank as the option and then searchabletext like output to file, and it would search through all of the manual pages for those terms. It might give you a long list of options that did that. But what it does is help you potentially find the command you can't remember. Another one is the command called Apropos, which again, searches based on the search text you gave so that it can look through all those pages and give you at least a list. And then you can say, "Oh yeah, that's thecommand, I see it there in the results." Then you can do the manual command on the current command and get the information you want. Now sometimes you don't want that much data, so you can use what's called the what is command. Let's say you know what LS kind of doesas a command, but you don't want to read page after page of documentation about the command, you just want to refresh your memory. What it does You would type whatisls and it gives you one line of printed information from the manual page that basically says "Here's the command; here's what it's generally supposed to do." Now, in some systems, what isdatabase may not exist. So you may need to run the make what is command first, which will go through all of the manual pages and create a what is database. Now, if you know the command LS, for example,you know what it does, but you also know it has some options, or what we sometimes call flags,and you don't know all of them. You could just type "help LS" and it will show you all of the options and syntax for that command. Or you can type in LS help to get the same type of information, but it was designed to show you the syntax and the options to help you understand how to type in the command. Now these documents, these manuals, you should find them under the path of User Share and Doc, so you can find them yourselves. If worst comes to worst, you can go find the information and the documentation that you're needing all on your own.

31. Man Page

Alright, we're gonna take a look at some other options we have for exploring our help needs. We saw in another demo how to use the manual command,but I want to remind you that you have, in fact, the K to help you in searching for help. And let's say we are wondering about the good news about zip utilities. So let's take a look at what that Mankay gives us, and they're showing us things that could match this entire category. For looking at the manualpages, we have the unzip zip zCAT. And so then, of course, they can say, "Allright, well, let's do a man of unzip." We didn't know we had that. And there's the page. Hit the letter Q to quit. Clear to clear my screen. Another command we said was this one called "Apropos." So we'll try Apprepo of Gzip and it gives us pretty much the same thing as the mank did to help us understand what's going on there as well as the different manuals that are available for us. All right, you've seen the LSD help. That was another way of getting the syntax of a command. In this case, the help was for the command LS. You could do this with most of your commands that are out there. But as a reminder, when I hit Enter, it just filled up the entire screen and scrolled off into oblivion. So I'd have to scroll up to read that entire help well instead. Now remember, the up arrow shows me the last help or the last command spacebar pipe more.You've seen this a couple of times for me by now if you've gotten an order and it's showing me the help now, but with the more button down at the bottom. So that's saying hit the Enter key to go line-by-line, hit the spacebar to move forward a page. But it makes reading it so much easier than having to just have it blow up your screen and then scroll up the queue again to quit. All right, so clear I like clear. I like to have a nice clean shell to work in. All right, another option, help LS. Some people say, "Well, what does that do?" Well, that says, "Hey, it doesn't work." So again, help doesn't necessarily work with allcommands, but that's where we put the help. Following the double dashes after the commands almost always gets you some topics. But at least it's telling you here that you can type in Help, Help, or Mankls and look at all of these things that match the words LS. Is that crazy? So again, you have some options for getting this help available to you. It's especially good when you just cannot remember the name of the command. That's where it's helpful to put that in. All right, some other commands we talked about, like whatis, and this time let's use a new command, echo. So Echo is a command that repeats something and displays it on your screen or monitor. We typed in "what is echo" and it shows us that it has got two options. It's a built-in command. It says that it echoes itself up here. If you run, it will display a line of text. Well, that's kind of what I said, but I think I used the term "spitting it out on your screen." But display is probably a nice way of putting it. You can now do help echo. Let's see what that does for us. Hey, now, that worked rather than doing the work. But that's why I said you're going to remember that if help, the command doesn't work, put in the command help. Unfortunately, though, again, it scrolled off my screen. So please assist echo pipe in providing it to me on a screen-by-screen basis. Well, okay, it said that the commandecho would display things on the screen. So let's type in "echo hello world." And there you have it. It put "hello world" on the screen. All right, so it did that for us. In fact, we did an example with echo and used one of those environmental variables with a random number generator. Okay, let's see what else we can do with some of these commands. LS is one of these that we've worked with and we've seen a lot of the commands that gave us the more and stuff like that.But let's try the LSF UserShare dock, and there are a lot of files there. You can just see them go screaming off the screen. So again, up arrow, more boom. It shows me that one page at a time. OK, so I'm going to hit the queue and stop looking at that particular put our settings.And what if I wanted to do a little bit more? In fact, let me hit the up arrow twice. Let me get that command to exactly list the files, right. Instead of putting in a series of left-to-right, top-to-bottom, it just ordered it as a single column. Now let's try the cat command. Now I'm going to type in catspace alt dot and notice what it did is that it gave me the same options that I had before, the same parameters from the previous command. It didn't put the entire previous command because the previous command was LS, but it put the parameters that I had. And now I can actually put Myfile here Myfile.I think there's one in there called Myfile. I can just finish it off and it will itspit out the contents of that particular file. So sometimes you might have a similar set of parameters that you want to use with a different command. That was the alt dot. It just repeated the parameters without putting in the command. So again, that's something else that might be helpful for you as well in working with your client command lines, getting help and knowing some of these really cool shortcuts.

32. Man Page Sections

Alright, so you can see we began the tour of Linux. The goal of this unit was to make sure you understood what the GUI was actually composed of, how it worked, how it interacted through X windows in the kernel, what some of the common applications are,and then also the command line interface, which I think a lot of you are going to get excited about as you get more experience. Now, if you've been around the Linux environment, you're probably saying, "Yes, the command line is the only way to go." I unfortunately fall into that dinosaur category. That command line is the only way to go because that's all I ever had. But I do like Gui's as well. If it saves you time, if it's easier to use,if it's consistent, you don't forget things in the commands. Use the gui's.It is the wave of our future. Anyway, whatever you choose, our goal was to make sure you saw them, that you understood what you could do, and if anything, got a good feel for both options. Maybe you'll utilise both options in working with the Linux operating system environment.

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