Get-Date -UFormat
Published May 27, 2019The Get-Date -UFormat parameter formats the date using Unix format. The full list of format specifiers are in the Notes section of the Get-Date help file.
Some examples are:
PS> Get-Date -UFormat '%Y-%m-%d %H:%M%:%S%Z'
2019-05-27 20:40:11+01
4 digit year – two digit month and day. Hour in 24 hour format and minutes and seconds and finally time zone as offset from GMT
Date in locale format
PS> Get-Date -UFormat %x
05/27/19
though it shows a US format for a UK locale?
PS> Get-Date -UFormat '%A %d %B %Y'
Monday 27 May 2019
day of week – day – Month (full name) 4 digit year.
Between the Format parameter and the UFormat parameter you should be able to get the date information into any format you require
Get-Date –Format
Published May 27, 2019Get-Date –Format enables you to control the formatting of the datetime object returned by the cmdlet.
A standard call to get date returns:
PS> Get-Date
27 May 2019 12:36:47
The –Format parameter takes a value from the DateTimeFormatInfo class - https://docs.microsoft.com/en-us/dotnet/api/system.globalization.datetimeformatinfo?view=netframework-4.8 – to specify how you want the information to be formatted.
For instance:
Short and long forms of the date with no time
PS> Get-Date -Format d
27/05/2019
PS> Get-Date -Format D
27 May 2019
Full date and short or long time
PS> Get-Date -Format f
27 May 2019 12:48
PS> Get-Date -Format F
27 May 2019 12:48:38
No year or time
PS> Get-Date -Format m
27 May
PS> Get-Date -Format M
27 May
RFC1123 compliant
PS> Get-Date -Format R
Mon, 27 May 2019 12:50:07 GMT
PS> Get-Date -Format r
Mon, 27 May 2019 12:50:10 GMT
Sortable
PS> Get-Date -Format s
2019-05-27T12:50:45
Short and long time only
PS> Get-Date -Format t
12:51
PS> Get-Date -Format T
12:51:14
Sortable Universal time
PS> Get-Date -Format u
2019-05-27 12:51:55Z
Z refers to the time zone
Specify day month year format
PS> Get-Date -Format 'dd/MM/yyyy'
27/05/2019
Exclusive OR
Published May 26, 2019PowerShell has a number of logical operators - - -and, –or, –not (or !). One I’ve really thought about is the exclusive OR operator –xor.
With a standard –or operator the result is TRUE if one of the statements is TRUE
PS> ('a' -eq 'A') -or ('a' -eq 'z')
True
The standard –or operator is also TRUE if both statements are true
PS> ('a' -eq 'A') -or ('Z' -eq 'z')
True
The exclusive OR is only TRUE when one of the statements is TRUE and the other is FALSE. So this returns TRUE
PS> ('a' -eq 'A') -xor ('a' -eq 'z')
True
But when both statements are TRUE it returns FALSE
PS> ('a' -eq 'A') -xor ('Z' -eq 'z')
False
The exclusive OR seems like bit of an oddity to me.
PowerShell has a bitwise xor operator -- -bxor but outside of that I’m struggling to find a use for –xor. Certainly as an admin I can’t think of a situation where I’d use it.
Just out curiosity have you used –xor and if so how?
Useful constants
Published May 26, 2019PowerShell provides easy access to some useful constants. I often see people calculating these values rather than using the constants.
PowerShell recognises kb, mb, gb, tb and pb for kilobyte, megabyte, gigabyte, terabyte and petabyte respectively. You can use them like this:
PS> 1kb; 1mb; 1gb, 1tb, 1pb
1024
1048576
1073741824
1099511627776
1125899906842624
Don’t leave a space between the value and the constant.
You can use them in calculations:
PS> 7247437567256292 / 1gb
6749702.21450207
PS> 7247437567256292 / 1tb
6591.50606884968
PS> 7247437567256292 / 1pb
6.43701764536101
Fractional values are allowed:
PS> 27.457gb
29481729261.568
You can use upper case or lower case to denote the constant
PS> 27.457gb
29481729261.568
PS> 27.457GB
29481729261.568
Next time you need to work with megabytes or other common constants don’t calculate them use the constants in PowerShell
Articles published in 2019
Published May 25, 2019I’ve had the following articles published in 2019
https://searchwindowsserver.techtarget.com/feature/Editing-content-with-Windows-PowerShell
Enjoy
Stable sort
Published May 25, 2019In Windows PowerShell if you do something like this:
PS> (1..20 | Sort-Object -Property {$_ % 3}) -join ' '
9 6 12 15 3 18 19 16 13 10 4 1 7 20 17 2 8 11 5 14
The results come back in an unexpected order. This is not a stable sort as the results are sorted by their modulus result but lose the order within each group.
If you want a stable sort – where the results come back from a calculation like this in the order in they were received you need to add the –Stable switch. BUT that was added to PowerShell v6.1 and later
PS> (1..20 | Sort-Object -Property {$_ % 3} -Stable ) -join ' '
3 6 9 12 15 18 1 4 7 10 13 16 19 2 5 8 11 14 17 20
The results are sorted by modulus result and correctly within each group of modulus results
You could also use the Top or Bottom parameters:
PS> (1..20 | Sort-Object -Property {$_ % 3} -Top 20 ) -join ' '
3 6 9 12 15 18 1 4 7 10 13 16 19 2 5 8 11 14 17 20
PS> (1..20 | Sort-Object -Property {$_ % 3} -Bottom 20 ) -join ' '
3 6 9 12 15 18 1 4 7 10 13 16 19 2 5 8 11 14 17 20
If you alter the values presented to Top and Bottom you’ll get a subset of the results
PS> (1..20 | Sort-Object -Property {$_ % 3} -Top 10 ) -join ' '
3 6 9 12 15 18 1 4 7 10
PS> (1..20 | Sort-Object -Property {$_ % 3} -Bottom 10 ) -join ' '
13 16 19 2 5 8 11 14 17 20
Sort-Object in PowerShell Core has an interesting set of additions compared to Windows PowerShell.
OpenSSH installation
Published May 25, 2019OpenSSH installation has got a lot simpler in Windows 10 1809; Windows Server 2019 and Windows Server 1809.
OpenSSH is available as an optional feature. The client is preinstalled when you install the operating system. You just need to install the server:
Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0
Installing the optional feature creates the required firewall rule which is good.
You still need to make changes to the sshd_config file to enable password and pubkey authentication. The subsystem isn’t configured for PowerShell.
There’s a bug in OpenSSH so that subsystem paths with spaces aren’t parsed so you need to create a symbolic link for the PowerShell v6 folder.
if you want to use key-pair authentication the OpenSSHUtils module on the PowerShell gallery has bugs so you need to manually set the permissions on the authorized_keys file.
SSH remoting has a lot to offer but incorrect documentation, the work needed to install and configure it and buggy software will stop people using it. On the plus side OpenSSH is getting easier to install and configure but its still a long way from good.
Create a symbolic link
Published May 23, 2019I recently had to create a symbolic link to overcome a bug in OpenSSH whereby OPENSSH won’t work with the path C:\Program Files\PowerShell\6\pwsh.exe because it has a space.
The answer is to create a symbolic link which is a file that contains a reference to another file (or directory):
New-Item -ItemType SymbolicLink -Path C:\pwsh -Target 'C:\Program Files\PowerShell\6'
C:\pwsh is the symbolic link and the Target parameter has the original path. You can now use C:\pwsh in place of C:\Program Files\PowerShell\6
New-Item can also create a Hardlink or a Junction.
HardLink is a directory entry that associates a name with a file on disk
Junction is an NTFS artefact that is a pointer to a directory on the local volume
PowerShell Core v6.2.1
Published May 21, 2019PowerShell Core v6.2.1 has been released - https://github.com/PowerShell/PowerShell/releases
as has v6.1.4
The new versions are to primarily fix the Security Vulnerability CVE-2019-0733 - https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0733
v6.2.1 also enables tab completion for functions
Windows Server 2019 updates with CIM
Published May 19, 2019Windows Server 2019 updates with CIM remain the same as all server versions post Windows Server 2016. This code will check for and install any updates. Micorosft Update or WSUS will be used depending on how your system is configured
$au = Invoke-CimMethod -Namespace root/microsoft/windows/windowsupdate -ClassName MSFT_WUOperations -MethodName ScanForUpdates -Arguments @{SearchCriteria="IsInstalled=0"}
$au.Updates
if ($au.Updates.Length -gt 0) {
Invoke-CimMethod -Namespace root/microsoft/windows/windowsupdate -ClassName MSFT_WUOperations -MethodName InstallUpdates -Arguments @{Updates = $au.Updates}
}
else {
Write-Warning "No updates available"
}
This code should work on Server 1709, 1803, 1809 and Windows Server 2019.
It won’t work on Windows Server 2016 as the CIM classes were changed post Windows Server 2016