9tail.myr

// A naive plan9 tail(1)-like implementation

use std
use bio


var		follow					// Watch and print further data
var		nlines					// Number of lines to print
var		out						// Buffered output


// Print usage information
const usage = {
	std.fput(1, "usage: tail [+-number[lbr]] [-f] [ file… ]\n")
	std.fatal("")
}

// Emit the lines of a file from a given line
const tail = {fd : std.fd
	var file	= bio.mkfile(fd, bio.Rd)
	var nnl		= 0
	var nbytes	= 0
	const nl	= ('\n' : byte)
	var targl : int	// Line to start printing from




	// Clean up
	bio.close(file)
	std.close(fd)
	bio.flush(out)
}


// Something vaguely tail(1) in Myrddin
const main = {argv : byte[:][:]
	nlines	= 10
	follow	= false

	// Commandline argument processing
	var i
	for i = 1; i < argv.len; i++
		match argv[i]
		| "-h":
			usage()
		| "-f":
			follow = true
		| "--":
			// Known end to arguments
			i++
			break
		| _:
			if (argv[i][0] : char) != ('-' : char) && (argv[i][0] : char) != ('+' : char)
				// Found a non-flag argument
				break
			;;

			// Handle -n[lbr] args
			// line, byte, rune ; line is the default

		;;

		std.put("→ {}\n", argv[i])
	;;

	var args = argv[i:]

	std.put("len = {}\n", args.len)

	out = bio.mkfile((1 : std.fd), bio.Wr)

	match args.len
	| 0:
		// Read from stdin if no [file] is specified
		tail((0 : std.fd))

	| _:
		// For each [file …] argument
		for file : args
			match std.open(file, std.Oread)
			| `std.Ok	fd:
				tail(fd)

			| `std.Err	err:
				std.fatal("err: could not open {} - {}\n", file, err)
			;;
		;;
	;;

	bio.close(out)
}