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<H2>Red Hat Linux Unleashed rhl14.htm</H2>
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<HR ALIGN=CENTER>
<P>
<UL>
<UL>
<UL>
<LI>
<A HREF="#E68E100" >Using the write Command</A>
<UL>
<LI>
<A HREF="#E69E198" >A Description of the write Command</A>
<LI>
<A HREF="#E69E199" >A Sample write Session</A>
<LI>
<A HREF="#E69E200" >write Etiquette</A></UL>
<LI>
<A HREF="#E68E101" >The talk Communication Tool</A>
<UL>
<LI>
<A HREF="#E69E201" >A Sample talk Session</A>
<LI>
<A HREF="#E69E202" >talk Etiquette</A></UL>
<LI>
<A HREF="#E68E102" >Electronic Mail</A>
<UL>
<LI>
<A HREF="#E69E203" >Mailboxes and Agents</A>
<LI>
<A HREF="#E69E204" >Understanding the Mail Message</A>
<LI>
<A HREF="#E69E205" >Types of Mail User Agents</A>
<UL>
<LI>
<A HREF="#E70E1" >Using elm</A>
<LI>
<A HREF="#E70E2" >Using Pine</A>
<LI>
<A HREF="#E70E3" >Using mailx (Berkeley Mail)</A></UL></UL>
<LI>
<A HREF="#E68E103" >Using news</A>
<UL>
<LI>
<A HREF="#E69E206" >nn</A>
<LI>
<A HREF="#E69E207" >tin</A>
<UL>
<LI>
<A HREF="#E70E4" >Command-Line Options</A></UL></UL>
<LI>
<A HREF="#E68E104" >Using FTP</A>
<UL>
<LI>
<A HREF="#E69E208" >Anonymous FTP</A>
<UL>
<LI>
<A HREF="#E70E5" >ftp Commands</A></UL></UL>
<LI>
<A HREF="#E68E105" >telnet</A>
<LI>
<A HREF="#E68E106" >Summary</A></UL></UL></UL>
<HR ALIGN=CENTER>
<A NAME="E66E14"></A>
<H1 ALIGN=CENTER>
<CENTER>
<FONT SIZE=6 COLOR="#FF0000"><B>14</B></FONT></CENTER></H1>
<BR>
<A NAME="E67E14"></A>
<H2 ALIGN=CENTER>
<CENTER>
<FONT SIZE=6 COLOR="#FF0000"><B>Using Communication Tools Under Linux</B></FONT></CENTER></H2>
<BR>
<P>The communication tools discussed in this chapter include the following:
<BR>
<UL>
<LI>write: For one-way communication with other users
<BR>
<BR>
<LI>mesg: For controlling message reception from other users
<BR>
<BR>
<LI>talk: For an interactive connection with other users
<BR>
<BR>
<LI>e-mail: For sending and receiving messages
<BR>
<BR>
<LI>telnet: For logging into remote sites
<BR>
<BR>
<LI>ftp: For remote file transfers
<BR>
<BR>
<LI>news: For reading news via nn and tin
<BR>
<BR>
</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.
<BR>
<BR>
<A NAME="E68E100"></A>
<H3 ALIGN=CENTER>
<CENTER>
<FONT SIZE=5 COLOR="#FF0000"><B>Using the </B><B>write</B><B> Command</B></FONT></CENTER></H3>
<BR>
<P>The write 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 her out to lunch, and you know that she is logged in, write is the tool to use. Unlike e-mail,
which is discussed later, write pastes your message directly on the recipient's terminal. The recipient does not have to take any steps to receive it.
<BR>
<P>To use the write command, your terminal and that of the other user should have write 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 tty command as shown here:
<BR>
<PRE>
<FONT COLOR="#000080">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 /dev/tty2. Your output may be different, depending on which terminal you happen to be on. The output of the ls command shows that others have write permission available on your terminal. You can confirm this
by using the mesg command as shown here:
<BR>
<PRE>
<FONT COLOR="#000080">mpsi:~$
mpsi:~$ mesg
Is y</FONT></PRE>
<P>The outcome of the mesg 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:
<BR>
<PRE>
<FONT COLOR="#000080">mpsi:~$ mesg n
mpsi:~$ mesg
Is n</FONT></PRE>
<P>The preceding segment turned the mesg off. Now you can't be disturbed by any other user. (You may miss out on lunch dates, though.)
<BR>
<BR>
<A NAME="E69E198"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>A Description of the </B><B>write</B><B> Command</B></FONT></CENTER></H4>
<BR>
<P>The write command enables you to write an actual message on the other terminal online. You have to issue the write command with the login ID of the user with whom you want to communicate. The write command informs the user at the other end that there is
a message from another user. write pastes that message onto the other user's terminal if their terminal's write permissions are set. Even if they are in the middle of an edit session, write 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. write is mostly used for one-way communication, but you can have an actual conversation as well.
<BR>
<BLOCKQUOTE>
<BLOCKQUOTE>
<HR ALIGN=CENTER>
<BR>
<NOTE>For the write command to work, mesg has to be turned on, so turn it back on.</NOTE>
<BR>
<HR ALIGN=CENTER>
</BLOCKQUOTE></BLOCKQUOTE>
<BR>
<A NAME="E69E199"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>A Sample </B><B>write</B><B> Session</B></FONT></CENTER></H4>
<BR>
<P>Because you want your friend to be able to write to your tty as well, always begin by checking the status of the mesg command:
<BR>
<PRE>
<FONT COLOR="#000080">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 who command and piping it to the grep program to search for Calvin, because you don't want the entire list of users to scroll down your terminal.
<BR>
<PRE>
<FONT COLOR="#000080">mpsi:~$ who | grep calvin
calvin tty2 Jan 15 15:26</FONT></PRE>
<BLOCKQUOTE>
<BLOCKQUOTE>
<HR ALIGN=CENTER>
<BR>
<NOTE>Don't forget to type /dev before the terminal name. Look at what happens when you don't type the /dev string:
<BR>mpsi:~$ ls -l tty2
<BR>ls: tty2: No such file or directory
<BR>Oops! All the ttys are in /dev, so add /dev to tty2.</NOTE>
<BR>
<HR ALIGN=CENTER>
</BLOCKQUOTE></BLOCKQUOTE>
<P>Now let's see whether he wants to be disturbed:
<BR>
<PRE>
<FONT COLOR="#000080">mpsi:~$ ls -al /dev/tty2
crw—w—w- 1 calvin users 4, 2 Jan 15 15:28 /dev/tty2
mpsi:~$</FONT></PRE>
<P>This excerpt shows you that Calvin is indeed logged in. Now let's see whether he is interested in communicating with a write session:
<BR>
<BR>
<PRE>
<FONT COLOR="#000080">mpsi:~$ write calvin</FONT></PRE>
<P>Calvin sees the following on his screen:
<BR>
<PRE>
<FONT COLOR="#000080">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:
<BR>
<PRE>
<FONT COLOR="#000080">mpsi:~$ write laurel
How are you?
Lunch tomorrow?</FONT></PRE>
<P>The following string appears on your terminal:
<BR>
<PRE>
<FONT COLOR="#000080">Message from calvin@mpsi on tty2 at 15:36 ...
How are you?
Lunch tomorrow?</FONT></PRE>
<P>You can answer Calvin by initiating another write session from your end and typing your message. You have to press Enter at the end of each line for it to be displayed at the other terminal. To simplify communications, you can type over at the logical
end of your sentence. Calvin should do likewise.
<BR>
<BR>
<A NAME="E69E200"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>write</B><B> Etiquette</B></FONT></CENTER></H4>
<BR>
<P>If you are waiting for the other party to respond to your write request, it is polite to let him reply while you wait. Only after he has accepted your invitation should the conversation begin. Also, let the called party have the first chance to reply by
typing hello or any other salutation. Avoid typing until the other party stops or signals you to begin with an end-of-message word, such as over. Remember, only one person can speak at a time on this channel.
<BR>
<BR>
<A NAME="E68E101"></A>
<H3 ALIGN=CENTER>
<CENTER>
<FONT SIZE=5 COLOR="#FF0000"><B>The </B><B>talk</B><B> Communication Tool</B></FONT></CENTER></H3>
<BR>
<P>The write tool was nice for communicating one at a time. However, Linux enables you to type simultaneously with the talk tool.
<BR>
<P>talk is an interactive communication tool that enables you to have an actual conversation in real-time mode with another user. You can actually see the conversation being typed as the other user is typing it. For talk to work, the other user has to be
logged in, just as in write.
<BR>
<P>talk can be very annoying and disturbing if someone wants to be pesky. If you don't want to be disturbed, just turn talk off by entering mesg n at the prompt.
<BR>
<BR>
<A NAME="E69E201"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>A Sample </B><B>talk</B><B> Session</B></FONT></CENTER></H4>
<BR>
<P>You can talk to somebody by typing talk followed by the user's login ID. To see if the user is logged in, you can use the who command just like you did for write. Let's try to talk to Calvin:
<BR>
<BR>
<PRE>
<FONT COLOR="#000080">$ talk calvin</FONT></PRE>
<P>The computer responds with
<BR>
<BR>
<PRE>
<FONT COLOR="#000080"> [Waiting for your party to respond]</FONT></PRE>
<P>The user on the other end sees the following message even if he is in the middle of an edit session. The system beeps and displays the following message on the terminal:
<BR>
<PRE>
<FONT COLOR="#000080">Message from Talk_Daemon@mpsi at 13:08 ...
talk: connection requested by laurel@hobbes.com.
talk: respond with: talk laurel@hobbes.com</FONT></PRE>
<P>To respond to this, type the command shown in the respond with message shown here. If your friend does not respond, the talk daemon persistently bothers him with the preceding message every 30 seconds.
<BR>
<P>At your terminal, you see the following messages:
<BR>
<PRE>
<FONT COLOR="#000080"> [Ringing your party again]
[Ringing your party again]
[Ringing your party again]
[Ringing your party again]</FONT></PRE>
<P>Occasionally you will see the following message:
<BR>
<BR>
<PRE>
<FONT COLOR="#000080"> [Your party is refusing messages]</FONT></PRE>
<P>What happened? Your friend at the other end does not want to talk or be disturbed. After several of your interruptions, he has decided to turn his mesg off. That is why you got the message that your party is refusing messages.
<BR>
<P>Now let's look at a nicer scenario, when someone wants to talk to you. He has to respond with the following command:
<BR>
<BR>
<PRE>
<FONT COLOR="#000080">talk laurel.</FONT></PRE>
<P>Then your terminal displays the following screen:
<BR>
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