Clean up ncurses mess in terminal after a crash

Question

I am drawing a TUI using ncurses. The trouble is that whenever my program gets seg-fault, my terminal is left in mess. I can not see what I am typing. Its a pain since I am

Answer 1

ncurses (any curses implementation) sets the terminal modes to raw and noecho while running, and allows applications to simulate these using the raw and noraw, echo and noecho functions. It does this for performance, to avoid waiting when switching between these modes.

When an application calls endwin, ncurses restores the terminal modes. It can also do this for reset_shell_mode, though endwin is used far more often.

If your application crashes, or exits without restoring the terminal modes using endwin, the most obvious problem is that you cannot see what you are typing, and that pressing enter does not work.

ncurses provides a signal handler to catch the user-initiated signals SIGINT, SIGTERM, and will cleanup when those are caught. It does not try to catch SIGSEGV because at that point, your application is dead and trying to resurrect it to repair things is counter productive.

Some people might advise using stty sane to restore the terminal modes. That "works", but on Unix platforms is likely to leave your erase key set to an unexpected value. It happens to work as expected for Linux- and modern BSD-systems.

However, beyond that, ncurses normally resets

• colors (default colors for the terminal)
• line-drawing (disabled)
• mouse protocol (to disable it)

If your application uses any of these features, then the reset command is the appropriate choice. It usually clears the screen as well (perhaps not what was wanted). And it uses fewer characters:

resetcontrolJ
stty sanecontrolJ

Further reading:

• Signal handlers in curs_initscr(3x)
• Portability in tput(1)
• reset - reinitialization