package main import ( "flag" "fmt" "io" "log" "os" "github.com/docker/distribution/version" "github.com/opencontainers/go-digest" ) var ( algorithm = digest.Canonical showVersion bool ) type job struct { name string reader io.Reader } func init() { flag.Var(&algorithm, "a", "select the digest algorithm (shorthand)") flag.Var(&algorithm, "algorithm", "select the digest algorithm") flag.BoolVar(&showVersion, "version", false, "show the version and exit") log.SetFlags(0) log.SetPrefix(os.Args[0] + ": ") } func usage() { fmt.Fprintf(os.Stderr, "usage: %s [files...]\n", os.Args[0]) fmt.Fprint(os.Stderr, ` Calculate the digest of one or more input files, emitting the result to standard out. If no files are provided, the digest of stdin will be calculated. `) flag.PrintDefaults() } func unsupported() { log.Fatalf("unsupported digest algorithm: %v", algorithm) } func main() { var jobs []job flag.Usage = usage flag.Parse() if showVersion { version.PrintVersion() return } var fail bool // if we fail on one item, foul the exit code if flag.NArg() > 0 { for _, path := range flag.Args() { fp, err := os.Open(path) if err != nil { log.Printf("%s: %v", path, err) fail = true continue } defer fp.Close() jobs = append(jobs, job{name: path, reader: fp}) } } else { // just read stdin jobs = append(jobs, job{name: "-", reader: os.Stdin}) } digestFn := algorithm.FromReader if !algorithm.Available() { unsupported() } for _, job := range jobs { dgst, err := digestFn(job.reader) if err != nil { log.Printf("%s: %v", job.name, err) fail = true continue } fmt.Printf("%v\t%s\n", dgst, job.name) } if fail { os.Exit(1) } }