#include <u.h>#include <libc.h> int	multi;int	nlines; intline(int fd, char *file){	char c;	int m, n, nalloc;	char *buf; 	nalloc = 0;	buf = nil;	for(m=0; ; ){		n = read(fd, &c, 1);		if(n < 0){			fprint(2, "read: error reading %s: %r\n", file);			exits("open");		}		if(n == 0)			break;		if(m == nalloc){			nalloc += 1024;			buf = realloc(buf, nalloc);			if(buf == nil){				fprint(2, "read: malloc error: %r\n");				exits("malloc");			}		}		buf[m++] = c;		if(c == '\n')			break;	}	if(m > 0)		write(1, buf, m);	free(buf);	return m;} voidlines(int fd, char *file){	do{		if(line(fd, file) == 0)			break;	}while(multi || --nlines>0);} voidmain(int argc, char *argv[]){	int i, fd;	char *s; 	ARGBEGIN{	case 'm':		multi = 1;		break;	case 'n':		s = ARGF();		if(s){			nlines = atoi(s);			break;		}		/* fall through */	default:		fprint(2, "usage: read [-m] [-n nlines] [files...]\n");		exits("usage");	}ARGEND 	if(argc == 0)		lines(0, "<stdin>");	else		for(i=0; i<argc; i++){			fd = open(argv[i], OREAD);			if(fd < 0){				fprint(2, "read: can't open %s: %r\n", argv[i]);				exits("open");			}			lines(fd, argv[i]);			close(fd);		} 	exits(0);}