- CTRL+S essentially does XOFF, which means the terminal will accept key strokes but won’t show the output of anything.
- It will act as if your terminal is dead when it’s certainly just waiting to be turned back on.
- CTRL+Q to turn flow-control on (XON).
- If you pressed a whole bunch of keys before pressing CTRL+Q, see the output from those keystrokes
- Ctrl-S is scroll-lock on, and Ctrl-Q is scroll lock off. This works in a lot of places on a lot of operating systems.
- Try this when booting or shutting down at a text screen.
- Chances are Ctrl-S will stop the scrolling messages. When done, press Ctrl-Q to continue.
- Ctrl-s and Ctrl-q are standard handshake protocols also refered to XOFF and XON.
- These are software handshake characters and there are also hardware handshake protocols using CTR/RTS lines.
- These protocols were used for modems and printers which were slower than the computer
- Pressing Ctrl-s inside vi editor or in Linux shell freezes the shell as it locks the terminal output.
- You need to press Ctrl-q to resume the terminal output.