docs: needs clarification: "terminal raw mode" (signal handling)

[jgehrcke]

About the SIGINT event on process it is said in the docs that

It is not generated when terminal raw mode is enabled.

https://github.com/nodejs/node/blame/3ec4b21b1c438255df6f1652377011080dc28052/doc/api/process.md#L504

In the example program I play around with the SIGINT handler was not firing. I assumed that I was testing with the "terminal raw mode", so I was looking into understanding what that is and how to disable it.

A web search for nodejs "terminal raw mode" didn't yield anything useful, though. I also explored node --help and didn't see anything obvious.

I think we should clarify in docs what "terminal raw mode" is and then cross-link to that place from the SIGINT doc I linked above.

[Fishrock123]

There is some documentation under the TTY docs: https://nodejs.org/dist/latest-v13.x/docs/api/tty.html#tty_readstream_setrawmode_mode

When in raw mode, input is always available character-by-character, not including modifiers. Additionally, all special processing of characters by the terminal is disabled, including echoing input characters. CTRL+C will no longer cause a SIGINT when in this mode.

I agree it should be linked to.