diff --git a/README.md b/README.md index c2e5a39..903d466 100644 --- a/README.md +++ b/README.md @@ -29,6 +29,7 @@ Contents: stealchain/ Dump the verified chain from a TLS connection. tlskeypair/ Check whether a TLS certificate and key file match. + utc/ Convert times to UTC. die/ Death of a program. fileutil/ Common file functions. lib/ Commonly-useful functions for writing Go programs. diff --git a/cmd/utc/README b/cmd/utc/README new file mode 100644 index 0000000..1084c00 --- /dev/null +++ b/cmd/utc/README @@ -0,0 +1,48 @@ +utc: convert times to UTC + +utc converts times to UTC. If no arguments are provided, prints the +current time in UTC. If the only time provided is "-", reads +newline-separated timestamps from standard input. + +Flags: + + -f format Go timezone format. See the Go documentation + (e.g. https://golang.org/pkg/time/#pkg-constants) + for an explanation of this format. + -z zone Text form of the time zone; this can be in short + time zone abbreviation (e.g. MST) or a location + (e.g. America/Los_Angeles). This has no effect + when printing the current time. + +Examples (note that the examples are done in the America/Los_Angeles / +PST8PDT time zone): + + + Getting the current time in UTC: + $ utc + 2016-06-14 14:30 = 2016-06-14 21:30 + + Converting a local timestamp to UTC: + $ utc '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-15 04:30 + + Converting a local EST timestamp to UTC (on a machine set to + PST8PDT): + $ utc -z EST '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-15 02:30 + + Converting timestamps in the form '14-06-2016 3:04PM': + $ utc -f '02-01-2006 3:04PM' '14-06-2016 9:30PM' + 14-06-2016 9:30PM = 15-06-2016 4:30AM + + Converting timestamps from standard input: + $ printf "2016-06-14 14:42\n2016-06-13 11:01" | utc - + 2016-06-14 14:42 = 2016-06-14 21:42 + 2016-06-13 11:01 = 2016-06-13 18:01 + + Converting a UTC timestamp to the local time zone: + $ utc -u '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-14 14:30 + + Converting a UTC timestamp to EST (on a machine set to + PST8PDT): + $ utc -u -z EST '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-14 16:30 + + + + + diff --git a/cmd/utc/main.go b/cmd/utc/main.go new file mode 100644 index 0000000..22f6e7b --- /dev/null +++ b/cmd/utc/main.go @@ -0,0 +1,162 @@ +package main + +import ( + "bufio" + "flag" + "fmt" + "io" + "os" + "time" +) + +var ( + format = "2006-01-02 15:04" // Format that will be used for times. + tz = "Local" // String descriptor for timezone. + fromLoc *time.Location // Go time.Location for the named timezone. + toLoc *time.Location // Go time.Location for output timezone. +) + +func usage(w io.Writer) { + fmt.Fprintf(w, `Usage: utc [-f format] [-u] [-h] [-z zone] [time(s)...] + +utc converts times to UTC. If no arguments are provided, prints the +current time in UTC. + +Flags: + + -f format Go timezone format. See the Go documentation + (e.g. https://golang.org/pkg/time/#pkg-constants) + for an explanation of this format. + + Default value: %s + + -h Print this help message. + + -u Timestamps are in UTC format and should be converted + to the timezone specified by the -z argument (which + defaults to '%s'). Note that this isn't particularly + useful with no arguments. + + -z zone Text form of the time zone; this can be in short + time zone abbreviation (e.g. MST) or a location + (e.g. America/Los_Angeles). This has no effect when + printing the current time. + + Default value: %s + +Examples (note that the examples are done in the America/Los_Angeles / +PST8PDT time zone): + + + Getting the current time in UTC: + $ utc + 2016-06-14 14:30 = 2016-06-14 21:30 + + Converting a local timestamp to UTC: + $ utc '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-15 04:30 + + Converting a local EST timestamp to UTC (on a machine set to + PST8PDT): + $ utc -z EST '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-15 02:30 + + Converting timestamps in the form '14-06-2016 3:04PM': + $ utc -f '02-01-2006 3:04PM' '14-06-2016 9:30PM' + 14-06-2016 9:30PM = 15-06-2016 4:30AM + + Converting timestamps from standard input: + $ printf "2016-06-14 14:42\n2016-06-13 11:01" | utc - + 2016-06-14 14:42 = 2016-06-14 21:42 + 2016-06-13 11:01 = 2016-06-13 18:01 + + Converting a UTC timestamp to the local time zone: + $ utc -u '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-14 14:30 + + Converting a UTC timestamp to EST (on a machine set to + PST8PDT): + $ utc -u -z EST '2016-06-14 21:30' + 2016-06-14 21:30 = 2016-06-14 16:30 + +`, format, tz, tz) +} + +func init() { + var help bool + var utc bool + + flag.Usage = func() { usage(os.Stderr) } + flag.StringVar(&format, "f", format, "time format") + flag.BoolVar(&help, "h", false, "print usage information") + flag.BoolVar(&utc, "u", false, "timestamps are in UTC format") + flag.StringVar(&tz, "z", tz, "time zone to convert from; if blank, the local timezone is used") + + flag.Parse() + + if help { + usage(os.Stdout) + os.Exit(0) + } + + if utc { + var err error + toLoc, err = time.LoadLocation(tz) + if err != nil { + fmt.Fprintf(os.Stderr, "Malformed timezone %s: %s\n", tz, err) + os.Exit(1) + } + + fromLoc = time.UTC + } else { + var err error + fromLoc, err = time.LoadLocation(tz) + if err != nil { + fmt.Fprintf(os.Stderr, "Malformed timezone %s: %s\n", tz, err) + os.Exit(1) + } + + toLoc = time.UTC + } +} + +func showTime(t time.Time) { + fmt.Printf("%s = %s\n", t.Format(format), t.In(toLoc).Format(format)) +} + +func dumpTimes(times []string) bool { + var errored bool + + for _, t := range times { + u, err := time.ParseInLocation(format, t, fromLoc) + if err != nil { + errored = true + fmt.Fprintf(os.Stderr, "Malformed time %s: %s\n", t, err) + continue + } + + showTime(u) + } + + return errored +} + +func main() { + var times []string + n := flag.NArg() + + switch n { + case 0: + showTime(time.Now()) + os.Exit(0) + case 1: + if flag.Arg(0) == "-" { + s := bufio.NewScanner(os.Stdin) + + for s.Scan() { + times = append(times, s.Text()) + } + } else { + times = flag.Args() + } + default: + times = flag.Args() + } + + if dumpTimes(times) { + os.Exit(1) + } +}