In Linux tutorial 1, I said that X offers the ability to display content on other hosts’ screens. This makes it possible to log in to a server that has a special program on it and have the display redirected to the screen in front of you. Allowing this to happen is a two-step process. The first step is telling your machine that it should allow connections from another host for X displays. This is done with the xhost command:

    [michael@workbox michael]$ xhost +ungerer

where ungerer is the name of the host you want to allow X displays to come from in addition to your own host. Now that you have allowed ungerer to display to your host, log in to ungerer, and set your DISPLAY environment variable like so:

    [michael@ungerer michael]$ DISPLAY="workbox:0"; export DISPLAY

This will redirect all X displays to the host workbox. If you have two hosts to try this with, an easy test to see if it worked is to start a web browser on the remote host and watch it display its content on your host. Neat trick, isn’t it? Once you are done with whatever work is required to allow other hosts to display to your screen, you need to explicitly disallow future connections like so:

    [michael@workbox michael]$ xhost -ungerer

If you want to disallow everyone, you can use the following shortcut:

    [michael@workbox michael]$ xhost -

CAUTION

Issuing the command xhost + is dangerous because it allows anyone to connect to your machine and display things on it. While this most often leads only to practical jokes, the potential for something more serious to happen is there. Be sure to specify from which hosts you allow X connections, and remember to undo it when you are done.

Mail Preferences: mail, pine, and mutt

Like everyone else, Linux folk need to read their e-mail. And as you can imagine, you have plenty of choices as to how. Although there are many GUI-based POP mail readers, this module covers command-line tools.

The one tool that you will always be able to find is called—you guessed it—mail. Simply run mail from the command line like so:

    [michael@workbox michael]$ mail

and you’ll see what mail you have available to read. Because this tool does not require any screen formatting, it is well suited for those instances where you are troubleshooting a host so broken it has no terminal control. To exit the mail program, type q and press ENTER. If you want more information about mail, check out its man page. As you’ll see, for a tool that looks very simple, it actually offers quite a bit of capability. Another popular tool is pine, which actually takes control of your terminal window and makes the display look much nicer. Being a fully menu-driven program where all of your options are always listed on a menu in front of you, pine tends to be a very popular choice for people new to UNIX. From a practical point of view, pine is ideal for communicating with people who use all sorts of other mail tools, since it understands all of the popular standards in use today (such as MIME attachments). The pine program also offers a very powerful filing system with which you can archive your mail easily and find it again at a later date. My personal favorite mail tool is mutt. To quote mutt’s author, “All mail clients suck. This one just sucks less.” mutt is another tool that looks simple on the outside but offers a wealth of capability. Unlike pine, mutt is much less menu-oriented. For folks who are used to the UNIX environment, this is a very welcome feature because it allows for very efficient use. Doubly useful is that mutt offers excellent memory management and can therefore handle extremely large mailboxes. More than once, I’ve used mutt to clean up someone’s mailbox that Outlook choked on. ftp Linux offers a very handy command-line version of the FTP client. Anyone used to theWindows version of the FTP client that runs under command.com will feel right at home with this, since theWindows version adopted the standard commands in use by the UNIX community since the late 70s. To start the FTP client, simply run ftp at the command line like so:

    [michael@workbox michael]$ ftp remotehostname

where remotehostname is the name of the host that you would like to FTP to/from.