#include <u.h>#include <libc.h> void	error(char *f, char *s);void	cat(int f, char *s); voidmain(int argc, char *argv[]){	int f, i; 	if(argc == 1)		cat(0, "<stdin>");	else for(i=1; i<argc; i++){		f = open(argv[i], OREAD);		if(f < 0)			error("cat: can't open %s: ", argv[i]);		else{			cat(f, argv[i]);			close(f);		}	}	exits(0);} voidcat(int f, char *s){	char buf[8192];	long n; 	while((n=read(f, buf, (long)sizeof buf))>0)		if(write(1, buf, n)!=n){			error("cat: write error copying %s: ", s);			return;		}} voiderror(char *f, char *s){	char buf[ERRLEN]; 	errstr(buf);	fprint(2, f, s);	fprint(2, "%s\n", buf);	exits("error");}