Hacking the history mechanism in rc

Hacking the history mechanism in rc

[Bruce Perens]

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I wanted to have a way to implement my own history
mechanism without hacking rc to bits, so I added
a "hook" for an external history mechanism. When my
version of rc is about to process a command line, it
checks to see if the user has defined an rc function
"add_history". If so, it calls the user function with
the command line in $1 . A simple definition of
add_history is:

fn add_history {
	echo -n $1 >> /usr/people/bruce/history_file
}

My version is a bit more complicated. It puts the
last command in the window title, etc.

I think this is a good change because:

	+ It replaces 15 lines of hard-coded C with four lines.
	+ It makes rc more versatile without adding code.
	+ It preserves the existing functionality.

I'm also experimenting with a "glob" function. The
function is called before globbing a filename, with a list containing
the arguments. If it recognizes any special characters that
it handles, it calls an external module that expands them
and returns the expanded list. I use this to implement ~name expansion
as in c-shell without adding code to rc. I was inspired by an old Version 6
or Version 7 Unix shell that used an external "glob" program.

I think there is a lot of room for work with "hook" functions.
Through them, rc can be made a lot more versatile without adding
code to rc itself.
				Bruce Perens