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Find out about others using Unix and "talk" to them | |
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| © July 29, 1996 | B-9 | |
Unix is a multi-user system. Many people can be (and usually are) logged in at the same time. It is possible to find out who else is currently logged in and even to communicate directly with another user.
The command who lists the SFU Computing ID of everyone who is currently logged in to the same host as you. For example, typing
whomight produce
jsmythe ttyp1 Jul 25 10:13 bbrown ttyp2 Jul 25 09:39 dlee ttyp3 Jul 24 20:30
The first column shows the SFU Computing ID of each user. The next column displays the "terminal" the person is using; this information isn't useful. The last column shows the date and time the person logged in.
To find out more about another ACS Unix user, use either the address_of command or the finger command. Each produces different information.
The address_of command is usually used to find a person's electronic mail address. It also gives you their SFU Computing ID, which you'll need in order to use the finger command most effectively.
To find the e-mail address and SFU Computing ID of Jane Doe, you would type
address_of jane doeThe result would look like
"Jane Doe"
Dept: English
Email: jdoe@sfu.ca
jane_doe@sfu.ca
Jane Doe's SFU Computing ID is jdoe and her e-mail address is either of the forms shown. You need not know the exact spelling of a person's name to use address_of. For more information about address_of and other ways to determine a person's e-mail address, see how-to M-2, Find someone's electronic mail address at SFU and elsewhere.
If you know someone's SFU Computing ID, the finger command with the -m option will tell you more about them. Typing
finger -m jdoeon Fraser might produce
Login name: jdoe In real life: Jan Doe Directory: /home/jdoe Shell: /bin/csh Last login at Fri Jul 2 10:13 from annex1.sfu.ca Project: To learn more about Unix Plan: To graduate by the year 2000
finger displays a person's SFU Computing ID, their name "in real life", their home directory, which Unix shell they use, the date and time they last logged in to the host (in this case, Fraser) and from where, and their project and plan (if they have these, see below). If the user is currently logged in to the host, finger will also show their idle time (the length of time since they last issued a command).
Note that if a person accesses their SFU Computing Account only from client e-mail programs like Eudora or Netscape, then finger will report that they have never logged in.
To have finger display information for your "Plan" and "Project", use a Unix editor like vi or emacs to create and edit two files in your home directory called .plan and .project. Note that the filenames must begin with a period. (For details on Unix editors, click here .) You'll also need to give others permission to read these files. To do this, type
chmod 644 .plan
chmod 644 .project
See how-to B-6, Permit Unix Files and Directories, for more information on the chmod command.
finger is capable of accessing remote systems; e.g., to find out about user jsmith on the cs.ubc.ca system, you would type
finger jsmith@cs.ubc.caDepending on the type of Unix system, finger may also report whether the user has any unread mail. (The reported last time that mail was read may not be accurate as it is affected by system programs for mail maintenance.)
For security or performance reasons, many Unix systems (including Fraser and Fraser) do not allow finger requests from other systems.
The who and finger commands give information about who other users are, but not about what they are doing. The command w displays additional information about users currently logged in and about the host computer.
Here is a typical w display:
The first line shows the time, how long the system has been up, the number of users logged into the system, and the load averages (how "busy" the system is, averaged over 1, 5 and 15 minutes).2:47pm up 8 days, 12:19, 26 users, load average: 1.21, 2.00, 2.79 User tty from login@ idle JCPU PCPU what jsmythe q4 dq21-nim2.sfu 12:54pm 1:05 3:27 1:32 elm bbrown q5 dq15-nim0.sfu 2:46pm 2:11 2:21 1:08 -csh
One line is displayed for each user currently logged in, showing their SFU Computing ID, the name of their "terminal", the host from which they are logged in, when they logged in, their idle time, the total CPU time used by that terminal so far (JCPU), and the CPU time used by the command now running (PCPU). The last column shows the command or process that the user is currently running.
Unix provides several ways to communicate with other users. Electronic mail is the most widely used mechanism. For more information on e-mail, click here .
Two other methods, write and talk, let you communicate directly with someone who is currently logged in. write and talk differ from e-mail because they send instant messages to a user who is currently logged in and they do not keep any record of the communication. Please be considerate of others when using write or talk to communicate with them.
When you know (by using the who command) that someone is logged in to the same host as you, you can send her/him an instant message by typing
write computingIDwhere computingID is the person's SFU Computing ID.
When you press Return, the other person will be notified that someone is contacting them (their screen may blink or they may hear a tone) and their screen will display
Message from jsmythe on ...Each line that you type will appear on the recipient's screen, until you type the interrupt character (usually Control-c). This breaks the connection and allows the recipient to resume work on other tasks. The recipient may need to press Return to get the Unix command prompt % again.
The write command allows only one-way communication between users on the same host. To set up a two-way exchange use the talk command. To initiate a conversation from Fraser with user bbrown on Fraser, user jdoe would type
talk bbrown@fraser.sfu.caThe recipient would be notified and would see
Message from Talk_Daemon@fraser.sfu.ca ...
talk: connection requested by jdoe@fraser.sfu.ca.
talk: respond with: talk jdoe@fraser.sfu.ca
To establish the connection, the recipient types what is shown on the last line. In the example above, bbrown would type
talk jdoe@fraser.sfu.ca
Each person's screen is divided in half. Whatever you type appears on the top half of your screen and on the bottom half of the other person's screen until you press Return. When you've concluded your conversation, either party can break the connection by typing the interrupt character (usually Control-c).
Note that the talk protocol is architecture dependent, and sometimes doesn't work between different types of Unix hosts.
If you don't want to be interrupted by someone trying to talk or write to you during your current login session, type
mesg nNow if someone tries to talk to you they will see
[Your party is refusing messages]
If someone tries to write to you they will see
write: Permission denied
When you're ready to receive talk and write communications again, type
mesg yIf you can't remember how mesg is set, type
mesgand Unix will reply with "is y" or "is n".
To permanently prohibit others from writing or talking to you, add the command
mesg n to the initialization file .mycshrc in your home directory. For more information on .mycshrc, see how-to B-14, Customize Your Unix Environment.
