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<H1></H1>



<UL>

	<LI><A HREF="#Heading1">- 14 -</A>

	<UL>

		<LI><A HREF="#Heading2">Communications Tools</A>

		<UL>

			<LI><A HREF="#Heading3">Using the write Command</A>

			<UL>

				<LI><A HREF="#Heading4">A Description of the write Command</A>

			</UL>

			<LI><A HREF="#Heading5">TIP</A>

			<UL>

				<LI><A HREF="#Heading6">A Sample write Session</A>

			</UL>

			<LI><A HREF="#Heading7">TIP</A>

			<UL>

				<LI><A HREF="#Heading8">write Etiquette</A>

			</UL>

			<LI><A HREF="#Heading9">The talk Communication Tool</A>

			<UL>

				<LI><A HREF="#Heading10">A Sample talk Session</A>

				<LI><A HREF="#Heading11">talk Etiquette</A>

			</UL>

			<LI><A HREF="#Heading12">Electronic Mail</A>

			<UL>

				<LI><A HREF="#Heading13">Mailboxes and Agents</A>

				<LI><A HREF="#Heading14">Understanding the Mail Message</A>

				<LI><A HREF="#Heading15">Types of Mail User Agents</A>

			</UL>

			<LI><A HREF="#Heading16">Listing 14.1. elms main screen</A>

			<LI><A HREF="#Heading17

			<LI><A HREF="#Heading18">Listing 14.2. Pines main screen</A>

			<LI><A HREF="#Heading19

			<LI><A HREF="#Heading20">Listing 14.3. Composing a message.</A>

			<LI><A HREF="#Heading21">Listing 14.4. Login notification of received mail</A>

			<LI><A HREF="#Heading22

			<LI><A HREF="#Heading23">Listing 14.5. Receiving mail</A>

			<LI><A HREF="#Heading24

			<LI><A HREF="#Heading25">Listing 14.6. Mail options</A>

			<LI><A HREF="#Heading26

			<LI><A HREF="#Heading27">Listing 14.7. Three received messages</A>

			<LI><A HREF="#Heading28

			<LI><A HREF="#Heading29">Using news</A>

			<UL>

				<LI><A HREF="#Heading30">nn</A>

				<LI><A HREF="#Heading31">tin</A>

			</UL>

			<LI><A HREF="#Heading32">TIP</A>

			<LI><A HREF="#Heading33">Listing 14.8. A sample tin session</A>

			<LI><A HREF="#Heading34

			<LI><A HREF="#Heading35">Listing 14.9. Another sample tin session</A>

			<LI><A HREF="#Heading36

			<LI><A HREF="#Heading37">Using FTP</A>

			<UL>

				<LI><A HREF="#Heading38">Anonymous FTP</A>

			</UL>

			<LI><A HREF="#Heading39">TIP</A>

			<LI><A HREF="#Heading40">Listing 14.10. An ftp session</A>

			<LI><A HREF="#Heading41

			<LI><A HREF="#Heading42">NOTE</A>

			<LI><A HREF="#Heading43">telnet</A>

			<LI><A HREF="#Heading44">Listing 14.11. Logging in via telnet</A>

			<LI><A HREF="#Heading45

			<LI><A HREF="#Heading46">Listing 14.12. Help for Archie</A>

			<LI><A HREF="#Heading47

			<LI><A HREF="#Heading48">Listing 14.13. Finding by keyword</A>

			<LI><A HREF="#Heading49

			<LI><A HREF="#Heading50">Listing 14.14. The output of the Archie command</A>

			<LI><A HREF="#Heading51

			<LI><A HREF="#Heading52">Summary</A>

		</UL>

	</UL>

</UL>



<P>

<HR SIZE="4">



<H2 ALIGN="CENTER"><A NAME="Heading1<FONT COLOR="#000077">- 14 -</FONT></H2>

<H2 ALIGN="CENTER"><A NAME="Heading2<FONT COLOR="#000077">Communications Tools</FONT></H2>

<P><I>by Uzma Husain</I></P>



<P>IN THIS CHAPTER</P>



<UL>

	<LI>Using the write Command 

	<P>

	<LI>The talk Communication Tool 

	<P>

	<LI>Electronic Mail

	<P>

	<LI>Using news 

	<P>

	<LI>Using FTP 

	<P>

	<LI>telnet 

</UL>



<P><BR>

The communication tools discussed in this chapter include the following:



<UL>

	<LI><TT>write</TT>: For one-way communication with other users

	<P>

	<LI><TT>mesg</TT>: For controlling message reception from other users

	<P>

	<LI><TT>talk</TT>: For an interactive connection with other users

	<P>

	<LI>e-mail: For sending and receiving messages

	<P>

	<LI><TT>telne</TT>t: For logging into remote sites

	<P>

	<LI><TT>ftp</TT>: For remote file transfers

	<P>

	<LI><TT>news</TT>: For reading news via <TT>nn</TT> and <TT>tin</TT>

</UL>



<P>This chapter discusses all of these communications tools in detail and gives you

the basics of how to use them in Linux. With practice, you will soon begin to use

these tools effectively.

<H3 ALIGN="CENTER"><A NAME="Heading3<FONT COLOR="#000077">Using the write Command</FONT></H3>

<P>The <TT>write</TT> command is a communication tool that enables a user to interact

directly with other users. If you want to ask your friend a simple question or ask

him out to lunch, and you know that he is logged in, <TT>write</TT> is the tool to

use. Unlike e-mail, which is discussed later, <TT>write</TT> pastes your message

directly on the recipient's terminal who does not have to take any steps to receive

it. To use the <TT>write</TT> command, your terminal and that of the other user should

have <TT>write</TT> permission. Having these permissions enables you to write messages

on each other's terminals. To look at the terminal settings, you need to know which

terminal you are on. To find your terminal number, use the <TT>tty</TT> command as

shown here:<FONT COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$ tty

/dev/tty2

mpsi:~$ ls -al /dev/tty2

crw--w--w-   1 calvin   users      4,   2 Jan 15 05:49 /dev/tty2

</FONT></PRE>

<P>The preceding code sample shows that I am on <TT>/dev/tty2</TT>. Your output may

be different, depending on which terminal you happen to be on. The output of the

<TT>ls</TT> command shows that others have <TT>write</TT> permission available on

your terminal. You can confirm this by using the <TT>mesg</TT> command as shown here:<FONT

COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$

mpsi:~$ mesg

Is y

</FONT></PRE>

<P>The outcome of the <TT>mesg</TT> command shows that the terminal enables messages

to be written to it. You can toggle the terminal settings on and off with the following

command:<FONT COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$ mesg n

mpsi:~$ mesg

Is n

</FONT></PRE>

<P>The preceding segment turned the <TT>mesg</TT> off. Now you can't be disturbed

by any other user. (You may miss out on lunch dates, though.)

<H4 ALIGN="CENTER"><A NAME="Heading4<FONT COLOR="#000077">A Description of

the write Command</FONT></H4>

<P>The <TT>write</TT> command enables you to write an actual message on the other

terminal online. You have to issue the <TT>write</TT> command with the login ID of

the user with whom you want to communicate. The <TT>write</TT> command informs the

user at the other end that there is a message from another user. <TT>write</TT> pastes

that message onto the other user's terminal if their terminal's <TT>write</TT> permissions

are set. Even if they are in the middle of an edit session, <TT>write</TT> overwrites

whatever is on the screen. The edit session contents are not corrupted; you can restore

the original screen on most editors with Ctrl-L. <TT>write</TT> is mostly used for

one-way communication, but you can have an actual conversation as well.



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading5<FONT COLOR="#000077"><B>TIP:</B> </FONT>For the <TT>write</TT>

	command to work, <TT>mesg</TT> has to be turned on, so turn it back on.

<HR>



</DL>



<H4 ALIGN="CENTER"><A NAME="Heading6<FONT COLOR="#000077">A Sample write Session</FONT></H4>

<P>Because you want your friend to be able to write to your <TT>tty</TT> as well,

always begin by checking the status of the <TT>mesg</TT> command:<FONT COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$

mpsi:~$ mesg

Is y

</FONT></PRE>

<P>Let's see whether your friend, Calvin, is logged in. You can do this by using

the <TT>who</TT> command and piping it to the <TT>grep</TT> program to search for

Calvin because you don't want the entire list of users to scroll down your terminal.<FONT

COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$ who | grep calvin

calvin   tty2     Jan 15 15:26

</FONT></PRE>



<DL>

	<DT><FONT COLOR="#0066FF"></FONT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading7<FONT COLOR="#000077"><B>TIP: </B></FONT>Don't forget to type

	<TT>/dev</TT> before the terminal name. Look at what happens when you don't type

	the <TT>/dev</TT> string:<FONT COLOR="#0066FF"></FONT>

</DL>





<DL>

	<DD><FONT COLOR="#0066FF">mpsi:~$ ls -l tty2<BR>

	ls: tty2: No such file or directory</FONT>

<HR>

<FONT COLOR="#0066FF"></FONT>

</DL>



<PRE><FONT COLOR="#0066FF"></FONT></PRE>





<BLOCKQUOTE>

	<P>Oops! All the <TT>tty</TT>s are in <TT>/dev</TT>, so add <TT>/dev</TT> to <TT>tty2</TT>.



</BLOCKQUOTE>



<P>Now let's see whether he wants to be disturbed:</P>

<PRE><FONT COLOR="#0066FF">

mpsi:~$ ls -al /dev/tty2

crw--w--w-   1 calvin   users      4,   2 Jan 15 15:28 /dev/tty2

mpsi:~$

</FONT></PRE>

<P>This excerpt shows you that Calvin is indeed logged in. Now let's see whether

he is interested in communicating with a <TT>write</TT> session:<FONT COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$ write calvin

</FONT></PRE>

<P>Calvin sees the following on his screen:<FONT COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$

Message from laurel@mpsi on tty1 at 15:36 ...

</FONT></PRE>

<P>Now you have to wait for Calvin's response to the request. He responds by typing

the following on his terminal if he is interested in communicating with you:<FONT

COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">mpsi:~$ write laurel

              How are you?

</FONT></PRE>



<PRE><FONT COLOR="#0066FF">          Lunch tomorrow?

</FONT></PRE>

<P>The following string appears on your terminal:<FONT COLOR="#0066FF"></FONT>

<PRE><FONT COLOR="#0066FF">Message from calvin@mpsi on tty2 at 15:36 ...

            How are you?

</FONT></PRE>



<PRE><FONT COLOR="#0066FF">            Lunch tomorrow?

</FONT></PRE>