Ytukyg

In my interactive bash shell run in lxterminal's window, I don't know what I have messed up.

Typing Return key doesn't start a new line, but Ctrl-C will.

$ ^C

$ $ $ $ $ ^C

$ ^C

$ $ $ $ $ $ $ 

When I type a command, although hitting Return key will execute it, the typed command is not visible.

Before that happened, I was running some command sudo lsof ... | less (or sudo netstat ... | less), and there seemed no output, so I hit ctrl-c and/or q multiple times in an arbitrary order. When I finally got out of less, that problem with bash happened.

Did I accidentally redirect the stdout of the shell somewhere else?

I don't want to close the shell, so is there some way to fix the problem? Thanks.

I think your terminal may be stuck in a “funny” mode. You probably can reset it with the /usr/bin/reset command, that normally comes with the ncurses library.

If reset (proposed in another answer) does not work, try:

stty sane

maybe followed by

tput rs1

I have the following alias defined (guess I picked it up somewhere on stackoverflow):

alias   fixtty='reset; stty sane; tput rs1; clear; echo -e "33c"'

As other answers suggest, simplest fix is just to run reset.

As to the cause though? This usually happens when you cat (or otherwise output) a binary file or data to your terminal.

Text is just text, and is not treated specially by the terminal, but there are also some special characters which aren't text, and are used to do things like move the cursor, clear the screen, change colour, stop echoing output, etc.

When you output binary data (rather than text), the terminal will see these special control characters and try to interpret them as they come through. You may notice the screen clears, flashes, or jumps around - this is all due to these control characters being honoured. You can experiment by running head /dev/urandom in a new terminal to see what I mean.

Most of the time, if your terminal is behaving weird in anyway, just running reset will fix it, by simply echoing all the special characters necessary to set the terminal into the basic default mode - e.g. there is a stop echoing input code and also a start echoing input code. The binary data has randomly included the former, which is why you can't see what your typing, and reset will include the latter (among others), which will fix it.