implement P;# Original by Steve Arons, based on Plan 9 p include "sys.m"; 	sys: Sys;	FD:	import Sys;include "draw.m";include "string.m";	str: String;include "bufio.m";	bufio: Bufio;	Iobuf: import bufio;include "sh.m"; stderr: ref FD;outb, cons: ref Iobuf;drawctxt: ref Draw->Context; nlines := 22;	# 1/3rd 66-line nroff page (!)progname := "p"; P: module{	init:  fn(ctxt:  ref Draw->Context, argv:  list of string);}; usage(){	sys->fprint(stderr, "Usage: p [-number] [file...]\n");	raise "fail:usage";} init(ctxt: ref Draw->Context, argv:  list of string){	sys = load Sys Sys->PATH;	bufio = load Bufio Bufio->PATH;	if(bufio == nil)		nomod(Bufio->PATH);	str = load String String->PATH;	if(str == nil)		nomod(String->PATH);	sys->pctl(Sys->FORKFD, nil);	drawctxt = ctxt; 	stderr = sys->fildes(2); 	if((stdout := sys->fildes(1)) != nil)		outb = bufio->fopen(stdout, bufio->OWRITE);	if(outb == nil){		sys->fprint(stderr, "p: can't open stdout: %r\n");		raise "fail:stdout";	}	cons = bufio->open("/dev/cons", bufio->OREAD);	if(cons == nil){		sys->fprint(stderr, "p: can't open /dev/cons: %r\n");		raise "fail:cons";	} 	if(argv != nil){		progname = hd argv;		argv = tl argv;		if(argv != nil){			s := hd argv;			if(len s > 1 && s[0] == '-'){				(x, y) := str->toint(s[1:],10);				if(y == "" && x > 0)					nlines = x;				else					usage();				argv = tl argv;			}		}	}	if(argv == nil)		argv = "-" :: nil;	for(; argv != nil; argv = tl argv){		file := hd argv;		fd: ref Sys->FD;		if(file == "-"){			file = "stdin";			fd = sys->fildes(0);		}else			fd = sys->open(file, Sys->OREAD);		if(fd == nil){			sys->fprint(stderr, "%s: can't open %s: %r\n", progname, file);			continue;		}		page(fd);		fd = nil;	}} nomod(m: string){	sys->fprint(sys->fildes(2), "%s: can't load %s: %r\n", progname, m);	raise "fail:load";} page(fd: ref Sys->FD){	inb := bufio->fopen(fd, bufio->OREAD);	nl := nlines;	while((line := inb.gets('\n')) != nil){		outb.puts(line);        		if(--nl == 0){			outb.flush();			nl = nlines;			pause();		}	}	outb.flush();   } pause(){	for(;;){		cmdline := cons.gets('\n');		if(cmdline == nil || cmdline[0] == 'q') # catch ^d			exit;		else if(cmdline[0] == '!') {			done := chan of int;			spawn command(cmdline[1:], done);			<-done;		}else			break;	}} command(cmdline: string, done: chan of int){	sh := load Sh Sh->PATH;	if(sh == nil) {		sys->fprint(stderr, "%s: can't load %s: %r\n", progname, Sh->PATH);		done <-= 0;		return;	}	sys->pctl(Sys->FORKFD, nil);	sys->dup(cons.fd.fd, 0);	sh->system(drawctxt, cmdline);	done <-= 1;}