funccat(f *os.File) { const NBUF = 512 var buf [NBUF]byte for { switch nr, err := f.Read(buf[:]); true { case nr < 0: fmt.Fprintf(os.Stderr, "cat: error reading: %s\n", err.Error()) os.Exit(1) case nr == 0: // EOF return case nr > 0: if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr { fmt.Fprintf(os.Stderr, "cat: error writing: %s\n", ew.Error()) } } } }
funcmain() { flag.Parse() // Scans the arg list and sets up flags if flag.NArg() == 0 { cat(os.Stdin) } for i := 0; i < flag.NArg(); i++ { f, err := os.Open(flag.Arg(i)) if f == nil { fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err) os.Exit(1) } cat(f) f.Close() } }