Improved time zone check.
Previously, the zone check compared time.Local and time.UTC. However, when this was tested on a machine that uses UTC locally, it became apparent that the two pointers can differ while having the same time zone. A more useful check is to look up the offsets for the time zones and compare those --- they'll return the same times.
This commit is contained in:
Kyle Isom
parent
57e31bfcf4
commit
c3909b92f1
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@ -1,9 +1,13 @@
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utc: convert times to UTC
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Usage: utc [-f format] [-u] [-h] [-z zone] [time(s)...]
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Usage: utc [-f format] [-h] [-o format] [-q] [-u] [-z zone] [time(s)...]
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utc converts times to UTC. If no arguments are provided, prints the
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current time in UTC.
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current time in UTC. If the only time provided is "-", reads newline-
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separated timestamps from standard input. If both the input and output
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timezones are the same (e.g., the local time zone is UTC), a warning
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message will be printed on standard error. This can be suppressed with
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the -q option.
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Flags:
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@ -13,12 +17,14 @@ Flags:
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Default value: 2006-01-02 15:04
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-h Print a help message.
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-h Print this help message.
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-o format Go timestamp format for outputting times. Uses the
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same format as the '-f' argument; it defaults to
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the same value as the '-f' argument.
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-q Suppress the timezone check warning message.
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-u Timestamps are in UTC format and should be converted
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to the timezone specified by the -z argument (which
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defaults to 'Local'). Note that this isn't particularly
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@ -61,6 +67,25 @@ PST8PDT time zone):
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+ Using a different output format:
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$ utc -o '2006-01-02T15:03:04MST' '2016-06-14 21:30'
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2016-06-14 21:30 = 2016-06-15T04:04:30UTC
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+ Example of the warning message when running utc on a machine
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where the local time zone is UTC:
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$ utc
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==================================================================
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Note: both input and output timezone offsets are the same --- this
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program may not do what you expect it to.
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(Converting from UTC (offset +0000) to UTC (offset +0000).)
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==================================================================
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2016-06-14 23:44 = 2016-06-14 23:44
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+ Example of the warning message when running utc on a machine
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where the local time zone is GMT:
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$ utc
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==================================================================
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Note: both input and output timezone offsets are the same --- this
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program may not do what you expect it to.
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(Converting from GMT (offset +0000) to UTC (offset +0000).)
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==================================================================
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2016-06-14 23:46 = 2016-06-14 23:46
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@ -10,19 +10,22 @@ import (
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)
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var (
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format = "2006-01-02 15:04" // Format that will be used for times.
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outFormat = format // Output format.
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tz = "Local" // String descriptor for timezone.
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fromLoc *time.Location // Go time.Location for the named timezone.
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toLoc *time.Location // Go time.Location for output timezone.
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format = "2006-01-02 15:04" // Format that will be used for times.
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outFormat = format // Output format.
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tz = "Local" // String descriptor for timezone.
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fromLoc *time.Location = time.Local // Go time.Location for the named timezone.
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toLoc *time.Location = time.UTC // Go time.Location for output timezone.
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)
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func usage(w io.Writer) {
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fmt.Fprintf(w, `Usage: utc [-f format] [-u] [-h] [-z zone] [time(s)...]
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fmt.Fprintf(w, `Usage: utc [-f format] [-h] [-o format] [-q] [-u] [-z zone] [time(s)...]
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utc converts times to UTC. If no arguments are provided, prints the
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current time in UTC. If the only time provided is "-", reads newline-
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separated timestamps from standard input.
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separated timestamps from standard input. If both the input and output
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timezones are the same (e.g., the local time zone is UTC), a warning
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message will be printed on standard error. This can be suppressed with
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the -q option.
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Flags:
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@ -38,6 +41,8 @@ Flags:
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same format as the '-f' argument; it defaults to
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the same value as the '-f' argument.
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-q Suppress the timezone check warning message.
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-u Timestamps are in UTC format and should be converted
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to the timezone specified by the -z argument (which
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defaults to '%s'). Note that this isn't particularly
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@ -80,23 +85,72 @@ PST8PDT time zone):
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+ Using a different output format:
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$ utc -o '2006-01-02T15:03:04MST' '2016-06-14 21:30'
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2016-06-14 21:30 = 2016-06-15T04:04:30UTC
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+ Example of the warning message when running utc on a machine
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where the local time zone is UTC:
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$ utc
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==================================================================
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Note: both input and output timezone offsets are the same --- this
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program may not do what you expect it to.
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(Converting from UTC (offset +0000) to UTC (offset +0000).)
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==================================================================
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2016-06-14 23:44 = 2016-06-14 23:44
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+ Example of the warning message when running utc on a machine
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where the local time zone is GMT:
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$ utc
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==================================================================
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Note: both input and output timezone offsets are the same --- this
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program may not do what you expect it to.
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(Converting from GMT (offset +0000) to UTC (offset +0000).)
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==================================================================
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2016-06-14 23:46 = 2016-06-14 23:46
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`, format, tz, tz)
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}
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func getZone(loc *time.Location) (string, int) {
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return time.Now().In(loc).Zone()
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}
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func checkZones(quiet bool) {
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if quiet {
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return
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}
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toZone, toOff := getZone(toLoc)
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fromZone, fromOff := getZone(fromLoc)
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if toOff == fromOff {
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fmt.Fprintf(os.Stderr, `
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==================================================================
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Note: both input and output timezone offsets are the same --- this
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program may not do what you expect it to.
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(Converting from %s (offset %+05d) to %s (offset %+05d).)
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==================================================================
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`, fromZone, fromOff, toZone, toOff)
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}
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}
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func init() {
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var help bool
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var utc bool
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var help, quiet, utc bool
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flag.Usage = func() { usage(os.Stderr) }
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flag.StringVar(&format, "f", format, "time format")
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flag.BoolVar(&help, "h", false, "print usage information")
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flag.StringVar(&outFormat, "o", outFormat, "output time format")
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flag.BoolVar(&quiet, "q", false, "suppress zone check warning")
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flag.BoolVar(&utc, "u", false, "timestamps are in UTC format")
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flag.StringVar(&tz, "z", tz, "time zone to convert from; if blank, the local timezone is used")
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flag.Parse()
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if help {
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if !utc {
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checkZones(quiet)
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}
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usage(os.Stdout)
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os.Exit(0)
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}
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@ -118,8 +172,14 @@ func init() {
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os.Exit(1)
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}
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if fromLoc == time.UTC {
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}
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toLoc = time.UTC
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}
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checkZones(quiet)
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}
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func showTime(t time.Time) {
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