implement Grep; include "sys.m";	sys: Sys;	FD: import Sys;	stdin, stderr, stdout: ref FD; include "draw.m";	Context: import Draw; include "regex.m";	regex: Regex;	Re: import regex; include "bufio.m";	bufio: Bufio;	Iobuf: import bufio; include "arg.m";  Grep: module{	init:	fn(ctxt: ref Context, argv: list of string);}; multi: int;lflag, nflag, vflag, iflag, Lflag, sflag: int = 0; badmodule(path: string){	sys->fprint(stderr, "grep: cannot load %s: %r\n", path);	raise "fail:bad module";} init(nil: ref Context, argv: list of string){	sys = load Sys Sys->PATH;	stdin = sys->fildes(0);	stdout = sys->fildes(1);	stderr = sys->fildes(2); 	arg := load Arg Arg->PATH;	if (arg == nil)		badmodule(Arg->PATH); 	regex = load Regex Regex->PATH;	if(regex == nil)		badmodule(Regex->PATH); 	bufio = load Bufio Bufio->PATH;	if(bufio == nil)		badmodule(Bufio->PATH); 	arg->init(argv);	while ((opt := arg->opt()) != 0) {		case opt {		'l' =>			lflag = 1;		'n' =>			nflag = 1;		'v' =>			vflag = 1;		'i' =>			iflag = 1;		'L' =>			Lflag = 1;		's' =>			sflag = 1;		* =>			usage();		}	}	argv = arg->argv();	arg = nil; 	if(argv == nil)		usage();	pattern := hd argv;	argv = tl argv;	if (iflag)		pattern = tolower(pattern);	(re, err) := regex->compile(pattern,0);	if(re == nil) {		sys->fprint(stderr, "grep: %s\n", err);		raise "fail:bad regex";	} 	matched := 0;	if(argv == nil)		matched = grep(re, bufio->fopen(stdin, Bufio->OREAD), "stdin");	else {		multi = (tl argv != nil);		for (; argv != nil; argv = tl argv) {			f := bufio->open(hd argv, Bufio->OREAD);			if(f == nil)				sys->fprint(stderr, "grep: cannot open %s: %r\n", hd argv);			else				matched += grep(re, f, hd argv);		}	}	if (!matched)		raise "fail:no matches";} usage(){	sys->fprint(stderr, "usage: grep [-lnviLs] pattern [file...]\n");	raise "fail:usage";} grep(re: Re, f: ref Iobuf, file: string): int{	matched := 0;	for(line := 1; ; line++) {		s := t := f.gets('\n');		if(s == nil)			break;		if (iflag)			s = tolower(s);		if((regex->executese(re, s, (0, len s-1), 1, 1) != nil) ^ vflag) {			matched = 1;			if(lflag || sflag) {				if (!sflag)					sys->print("%s\n", file);				return matched;			}			if (!Lflag) {				if(nflag)					if(multi)						sys->print("%s:%d: %s", file, line, t);					else						sys->print("%d:%s", line, t);				else					if(multi)						sys->print("%s: %s", file, t);					else						sys->print("%s", t);			}		}	}	if (Lflag && matched == 0 && !sflag)		sys->print("%s\n", file);	return matched;} tolower(s: string): string{	for (i := 0; i < len s; i++) {		c := s[i];		if (c >= 'A' && c <= 'Z')			s[i] = c - 'A' + 'a';	}	return s;}