Learning the UNIX Operating System, Fourth Edition

The Unresponsive Terminal

During your UNIX session (while you’re logged in), your terminal may not respond when you type a command, or the display on your screen may stop at an unusual place. That’s called a “hung” or “frozen” terminal or session.

A session can be hung for several reasons. One of the most common is that the connection between your terminal and the computer gets too busy and your terminal has to wait its turn. (Other users or computers are probably sharing the same connection.) In that case, your session will start by itself in a few moments. You should not try to “un-hang” the session by entering extra commands because those commands will all take effect after the connection resumes.

If the system doesn’t respond for quite a while (and how long that is depends on your individual situation; ask your system administrator for advice), the following solutions will usually work. Try these in the order shown until the system responds.

1. Press the RETURN key.

   You may have typed a command but forgotten to press RETURN to tell the shell that you’re done typing and it should now interpret the command.

2. If you can type commands, but nothing happens when you press RETURN, try pressing LINE FEED or typing CTRL-J. If this works, your terminal needs to be reset to fix the RETURN key. Some systems have a reset command that you can run by typing CTRL-J reset CTRL-J. If this doesn’t work, you may need to log out and log back in or turn your terminal off and on again.

3. If your shell ...