Problems with Terminals
Here are a lot of techniques for unlocking a
locked-up terminal or window session.
If your terminal has a HOLD SCREEN or SCROLL LOCK button, did you
accidentally press it?
Try pressing it and see if things start working.
If pressing the button once doesn't fix the problem, you should probably press
it once more to undo the screen hold.
Otherwise, you may lock up your session worse than it was before!
Another way to stop output is by pressing
The way to restart stopped output is with
CTRL-q - try
pressing that now.
button, though, if
doesn't help, you don't need
to undo it.)
If you have a
shell prompt (7.1
instead of being in the program you thought you
were running - and
if your UNIX has job control - you may have stopped a job.
Try the jobs
command; if the job is stopped, restart it . (12.8
The program may be waiting for you to answer a question or type text
to its standard input.
If the program you were running does something that's hard to undo-like
try this step unless you've thought about it
If your system has
you can find out by putting the job in the background with
If the job was waiting for input, you'll see the message:
 + Stopped (tty input) grep pat
bring the job back into the foreground and answer its question,
if you know what that question is.
Otherwise, now that the job is stopped, you can kill it.
See the following directions.
On systems without job control, you may be able to satisfy the program by
or some other key that the program is expecting, like y
You could also try pressing [CTRL-d]
or whatever your
"end of input" character is set to.
That might log you out, though, unless you've set the
If your terminal is hooked to a computer, modem, or network, be sure that
the wires haven't come loose.
If you're using a modem and the modem has function lights, try pressing
keys and see if the SD or Send Data light flashes.
If it does, your terminal is sending data to the host computer.
If the RD or Receive Data light flashes, the computer is sending data to your
terminal-if you don't see anything, there might be something wrong on your
If you're connected with
the network to the remote computer might be down or be really slow.
Try opening another connection to the same remote host-if you get a response
, you have two choices:
Wait for your original connection to unfreeze.
The connection may come back and let you keep working where
you left off.
Or the connection may end when rlogin
the network problem.
Quit the session and try later.
To abort a program, most users press
Your account may be set up to use a different interrupt
character, like DELETE or RUBOUT.
If these don't work, try
Under most circumstances,
this will force the program to terminate.
Otherwise, do the following:
Log in at another terminal or window.
Enter the command
On System V, use
is your UNIX username.
This displays a list of the
programs you are running, something like this:
PID TTY STAT TIME COMMAND
163 i26 I 0:41 -csh (csh)
8532 i26 TW 2:17 vi ts.ms
22202 i26 S 12:50 vi UNIXintro.ms
8963 pb R 0:00 ps -x
24077 pb S 0:05 -bin/csh (csh)
Search through this list to find the command that has backfired.
Note the process identification (PID) number for this command.
Enter the command
is the identification number from the previous step.
If that doesn't work, try
to send a
You may need kill -9
, but try the other kill
If the UNIX shell prompt (like
has appeared at your
original terminal, things are probably back to normal.
You may still have to
take the terminal out of a strange mode (42.4
If the shell prompt hasn't come back, find the shell
associated with your terminal (identified by a tty number) and
The command name for the C shell is csh
For the Bourne shell, it is sh
In most cases, this will destroy
any other commands running from your terminal.
Be sure to kill
the shell on your own terminal, not the terminal you borrowed to
enter these commands.
The tty you borrowed is the one running ps
; look at
the example above and check the
In this case, the borrowed terminal is TTYpb.
to ensure that your shell has died.
If it is still there,
take more drastic action with the command
Run ps -x
again to be sure that all processes on the other tty
(In some cases, processes will remain.)
If there are still processes on the other tty, kill them.
At this point, you should be able to log in again from your own terminal.
which lists all the programs you are running,
also gives you useful information about the status of each program and
the amount of CPU time it has consumed.
Note that ps
all the programs you are running, including programs you may
not know about (e.g., programs that other programs execute automatically).