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 2016-06-14 16:42:33 -07:00
parent 57e31bfcf4
commit c3909b92f1
2 changed files with 100 additions and 15 deletions

View File

@ -1,9 +1,13 @@
utc: convert times to UTC
Usage: utc [-f format] [-u] [-h] [-z zone] [time(s)...]
Usage: utc [-f format] [-h] [-o format] [-q] [-u] [-z zone] [time(s)...]
utc converts times to UTC. If no arguments are provided, prints the
current time in UTC.
current time in UTC. If the only time provided is "-", reads newline-
separated timestamps from standard input. If both the input and output
timezones are the same (e.g., the local time zone is UTC), a warning
message will be printed on standard error. This can be suppressed with
the -q option.
Flags:
@ -13,12 +17,14 @@ Flags:
Default value: 2006-01-02 15:04
-h Print a help message.
-h Print this help message.
-o format Go timestamp format for outputting times. Uses the
same format as the '-f' argument; it defaults to
the same value as the '-f' argument.
-q Suppress the timezone check warning message.
-u Timestamps are in UTC format and should be converted
to the timezone specified by the -z argument (which
defaults to 'Local'). Note that this isn't particularly
@ -61,6 +67,25 @@ PST8PDT time zone):
+ Using a different output format:
$ utc -o '2006-01-02T15:03:04MST' '2016-06-14 21:30'
2016-06-14 21:30 = 2016-06-15T04:04:30UTC
+ Example of the warning message when running utc on a machine
where the local time zone is UTC:
$ utc
==================================================================
Note: both input and output timezone offsets are the same --- this
program may not do what you expect it to.
(Converting from UTC (offset +0000) to UTC (offset +0000).)
==================================================================
2016-06-14 23:44 = 2016-06-14 23:44
+ Example of the warning message when running utc on a machine
where the local time zone is GMT:
$ utc
==================================================================
Note: both input and output timezone offsets are the same --- this
program may not do what you expect it to.
(Converting from GMT (offset +0000) to UTC (offset +0000).)
==================================================================
2016-06-14 23:46 = 2016-06-14 23:46

View File

@ -13,16 +13,19 @@ var (
format = "2006-01-02 15:04" // Format that will be used for times.
outFormat = format // Output format.
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.
fromLoc *time.Location = time.Local // Go time.Location for the named timezone.
toLoc *time.Location = time.UTC // Go time.Location for output timezone.
)
func usage(w io.Writer) {
fmt.Fprintf(w, `Usage: utc [-f format] [-u] [-h] [-z zone] [time(s)...]
fmt.Fprintf(w, `Usage: utc [-f format] [-h] [-o format] [-q] [-u] [-z zone] [time(s)...]
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.
separated timestamps from standard input. If both the input and output
timezones are the same (e.g., the local time zone is UTC), a warning
message will be printed on standard error. This can be suppressed with
the -q option.
Flags:
@ -38,6 +41,8 @@ Flags:
same format as the '-f' argument; it defaults to
the same value as the '-f' argument.
-q Suppress the timezone check warning 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
@ -80,23 +85,72 @@ PST8PDT time zone):
+ Using a different output format:
$ utc -o '2006-01-02T15:03:04MST' '2016-06-14 21:30'
2016-06-14 21:30 = 2016-06-15T04:04:30UTC
+ Example of the warning message when running utc on a machine
where the local time zone is UTC:
$ utc
==================================================================
Note: both input and output timezone offsets are the same --- this
program may not do what you expect it to.
(Converting from UTC (offset +0000) to UTC (offset +0000).)
==================================================================
2016-06-14 23:44 = 2016-06-14 23:44
+ Example of the warning message when running utc on a machine
where the local time zone is GMT:
$ utc
==================================================================
Note: both input and output timezone offsets are the same --- this
program may not do what you expect it to.
(Converting from GMT (offset +0000) to UTC (offset +0000).)
==================================================================
2016-06-14 23:46 = 2016-06-14 23:46
`, format, tz, tz)
}
func getZone(loc *time.Location) (string, int) {
return time.Now().In(loc).Zone()
}
func checkZones(quiet bool) {
if quiet {
return
}
toZone, toOff := getZone(toLoc)
fromZone, fromOff := getZone(fromLoc)
if toOff == fromOff {
fmt.Fprintf(os.Stderr, `
==================================================================
Note: both input and output timezone offsets are the same --- this
program may not do what you expect it to.
(Converting from %s (offset %+05d) to %s (offset %+05d).)
==================================================================
`, fromZone, fromOff, toZone, toOff)
}
}
func init() {
var help bool
var utc bool
var help, quiet, utc bool
flag.Usage = func() { usage(os.Stderr) }
flag.StringVar(&format, "f", format, "time format")
flag.BoolVar(&help, "h", false, "print usage information")
flag.StringVar(&outFormat, "o", outFormat, "output time format")
flag.BoolVar(&quiet, "q", false, "suppress zone check warning")
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 {
if !utc {
checkZones(quiet)
}
usage(os.Stdout)
os.Exit(0)
}
@ -118,8 +172,14 @@ func init() {
os.Exit(1)
}
if fromLoc == time.UTC {
}
toLoc = time.UTC
}
checkZones(quiet)
}
func showTime(t time.Time) {