Is it possible to use arrow key in lex yacc ?

Question

I developed for my university a mini-shell. For parse the command line I use lex and yacc.

When I press up/down/left/right arrow the string "^[[A or B or C or D is displayed.

Is it possible to recognize this character for execute action when this key is pressed ? Maybe using the functions of ncurses library (I'm in Linux)?

I show, the bash use yacc grammar ( https://en.wikipedia.org/wiki/GNU_bison ) and we can use the arrow key. So I think is possible.

Thank you.

Answer 1

You could...

Essentially, yacc provides you with a state machine using terminal tokens (symbolic constants) provided by lex. Think of it as a big switch statement.

The arrow-keys returned by curses (if you call keypad) are defined in the curses header file as symbolic constants, e.g., KEY_UP, KEY_HOME, etc. There's a list in the getch manual page.

The curses library reads the character sequences, using its own state machine, matches the sequences against the terminal description and returns the constants.

Whether you get constants from lex or curses doesn't really matter much. yacc doesn't care. Also, whether you even use lex in this case, or just call getch directly may not matter (depending on how you have organized your program).

But most people wouldn't bother with lex/yacc for parsing editing sequences on the input buffer.