tz_windows.go

Documentation: github.com/thlib/go-timezone-local/tzlocal

     1  package tzlocal
     2  
     3  //go:generate go run ./../tzlocal/cmd/update_tzmapping.go
     4  
     5  import (
     6  	"fmt"
     7  	"os/exec"
     8  	"strings"
     9  
    10  	"golang.org/x/sys/windows/registry"
    11  )
    12  
    13  const tzKey = `SYSTEM\CurrentControlSet\Control\TimeZoneInformation`
    14  const tzKeyVal = "TimeZoneKeyName"
    15  
    16  // LocalTZ obtains the name of the time zone Windows is configured to use. Returns the corresponding IANA standard name
    17  func LocalTZ() (string, error) {
    18  	var winTZname string
    19  	var errTzutil, errReg error
    20  
    21  	// try tzutil command first - if that is not available, try to read from registry
    22  	winTZname, errTzutil = localTZfromTzutil()
    23  	if errTzutil != nil {
    24  		winTZname, errReg = localTZfromReg()
    25  		if errReg != nil { // both methods failed, return both errors
    26  			return "", fmt.Errorf("failed to read time zone name with errors\n(1) %s\n(2) %s", errTzutil, errReg)
    27  		}
    28  	}
    29  
    30  	if name, ok := WinTZtoIANA[winTZname]; ok {
    31  		return name, nil
    32  	}
    33  	return "", fmt.Errorf("could not find IANA tz name for set time zone \"%s\"", winTZname)
    34  }
    35  
    36  // localTZfromTzutil executes command `tzutil /g` to get the name of the time zone Windows is configured to use.
    37  func localTZfromTzutil() (string, error) {
    38  	cmd := exec.Command("tzutil", "/g")
    39  	data, err := cmd.Output()
    40  	if err != nil {
    41  		return "", err
    42  	}
    43  	return strings.TrimSpace(string(data)), nil
    44  }
    45  
    46  // localTZfromReg obtains the time zone Windows is configured to use from registry.
    47  func localTZfromReg() (string, error) {
    48  	k, err := registry.OpenKey(registry.LOCAL_MACHINE, tzKey, registry.QUERY_VALUE)
    49  	if err != nil {
    50  		return "", err
    51  	}
    52  	defer k.Close()
    53  
    54  	winTZname, _, err := k.GetStringValue(tzKeyVal)
    55  	if err != nil {
    56  		return "", err
    57  	}
    58  	return strings.TrimSpace(winTZname), nil
    59  }
    60
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