package main /* * Computes md5 sums for files listed on the command line. Similar to the * Unix md5sum utility. Largely stolen and adapted from an offical Go example. * https://golang.org/pkg/crypto/md5/#pkg-examples */ import ( "crypto/md5" "fmt" "os" "io" ) func process(fn string) { // Open the file, print a message and bail if the open fails. fi, err := os.Open(fn) if err != nil { fmt.Println(fn+":",err) return } // Here's a nice use of defer. The file will get closed // after we're done, whether we leave by error or normally. defer fi.Close() // This object accumulates the sum. h := md5.New() // We'll copy the data ourselves. (Original uses a higher-level // call that essentially does all this in one line.) for { // Read a block of data from the file. var data [256]byte n, err := fi.Read(data[:]) if n == 0 && err == io.EOF { break } else if(err != nil) { fmt.Println(fn+":",err) return } // Write it to the summer. The hash object implements // a frequently-used interface io.Writer which contains // the Write method and some others. h.Write(data[0:n]) } fmt.Printf("%032x %s\n", h.Sum(nil), fn) } func main() { for _,fn := range(os.Args[1:]) { process(fn) } }