Cannot change LastWriteTime or LastAccessTime of a symlink

[Liturgist]

Description

It does not appear to be possible to change the LastWriteTime or LastAccessTime of a symlink. It works on hardlinks.

PS C:\src\t> $SleepTime = 61
PS C:\src\t> $BaseDir = 'C:\src\t'
PS C:\src\t> $BaseFile = Join-Path -Path $BaseDir -ChildPath 'yy.txt'
PS C:\src\t> $SymlinkFile = Join-Path -Path $BaseDir -ChildPath 'yy-slink.txt'
PS C:\src\t> $HardlinkFile = Join-Path -Path $BaseDir -ChildPath 'yy-hlink.txt'
PS C:\src\t> if (Test-Path -Path $BaseFile) { Remove-Item -Path $BaseFile }
PS C:\src\t> if (Test-Path -Path $SymlinkFile) { Remove-Item -Path $SymlinkFile }
PS C:\src\t> if (Test-Path -Path $HardlinkFile) { Remove-Item -Path $HardlinkFile }
PS C:\src\t> New-Item -Path $BaseFile -ItemType File -Value "this is a new file`r`n"


    Directory: C:\src\t

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---          2020-07-06    14:23             20 yy.txt

PS C:\src\t> New-Item -ItemType SymbolicLink -Path $SymlinkFile -Target $BaseFile


    Directory: C:\src\t

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
la---          2020-07-06    14:23              0 yy-slink.txt -> C:\src\t\yy.txt

PS C:\src\t> Get-ChildItem -Path 'C:\src\t' -Filter 'yy*.txt' | Format-List 'Name','*Time'

Name           : yy.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:23:41
LastWriteTime  : 2020-07-06 14:23:41

Name           : yy-slink.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:23:41
LastWriteTime  : 2020-07-06 14:23:41


PS C:\src\t> Start-Sleep -Seconds $SleepTime
PS C:\src\t> $NewTimestamp = Get-Date
PS C:\src\t> Set-ItemProperty -Path $SymlinkFile -Name LastAccessTime -Value $NewTimestamp
PS C:\src\t> Set-ItemProperty -Path $SymlinkFile -Name LastWriteTime -Value $NewTimestamp
PS C:\src\t> Start-Sleep -Seconds 5
PS C:\src\t> Get-ChildItem -Path $BaseDir -Filter 'yy*.txt' | Format-List 'Name','*Time'

Name           : yy.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:24:42
LastWriteTime  : 2020-07-06 14:24:42

Name           : yy-slink.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:23:41
LastWriteTime  : 2020-07-06 14:23:41


PS C:\src\t> & cmd.exe /C "DIR /TA yy*"
 Volume in drive C has no label.
 Volume Serial Number is 0E33-300C

 Directory of C:\src\t

2020-07-06  14:23    <SYMLINK>      yy-slink.txt [C:\src\t\yy.txt]
2020-07-06  14:24                20 yy.txt
               2 File(s)             20 bytes
               0 Dir(s)  739,939,135,488 bytes free
PS C:\src\t> & cmd.exe /C "DIR /TW yy*"
 Volume in drive C has no label.
 Volume Serial Number is 0E33-300C

 Directory of C:\src\t

2020-07-06  14:23    <SYMLINK>      yy-slink.txt [C:\src\t\yy.txt]
2020-07-06  14:24                20 yy.txt
               2 File(s)             20 bytes
               0 Dir(s)  739,939,135,488 bytes free
PS C:\src\t> New-Item -ItemType HardLink -Path $HardlinkFile -Target $BaseFile


    Directory: C:\src\t

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---          2020-07-06    14:24             20 yy-hlink.txt

PS C:\src\t> Get-ChildItem -Path $BaseDir -Filter 'yy*.txt' | Format-List 'Name','*Time'

Name           : yy.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:24:42
LastWriteTime  : 2020-07-06 14:24:42

Name           : yy-hlink.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:24:42
LastWriteTime  : 2020-07-06 14:24:42

Name           : yy-slink.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:23:41
LastWriteTime  : 2020-07-06 14:23:41


PS C:\src\t> Start-Sleep -Seconds $SleepTime
PS C:\src\t> $NewTimestamp = Get-Date
PS C:\src\t> Set-ItemProperty -Path $HardlinkFile -Name LastAccessTime -Value $NewTimestamp
PS C:\src\t> Set-ItemProperty -Path $HardlinkFile -Name LastWriteTime -Value $NewTimestamp
PS C:\src\t> Start-Sleep -Seconds 5
PS C:\src\t> Get-ChildItem -Path $BaseDir -Filter 'yy*.txt' | Format-List 'Name','*Time'

Name           : yy.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:24:42
LastWriteTime  : 2020-07-06 14:24:42

Name           : yy-hlink.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:25:50
LastWriteTime  : 2020-07-06 14:25:50

Name           : yy-slink.txt
CreationTime   : 2020-07-06 14:23:41
LastAccessTime : 2020-07-06 14:23:41
LastWriteTime  : 2020-07-06 14:23:41


PS C:\src\t> & cmd.exe /C "DIR /TA yy*"
 Volume in drive C has no label.
 Volume Serial Number is 0E33-300C

 Directory of C:\src\t

2020-07-06  14:25                20 yy-hlink.txt
2020-07-06  14:23    <SYMLINK>      yy-slink.txt [C:\src\t\yy.txt]
2020-07-06  14:24                20 yy.txt
               3 File(s)             40 bytes
               0 Dir(s)  739,939,672,064 bytes free
PS C:\src\t> & cmd.exe /C "DIR /TW yy*"
 Volume in drive C has no label.
 Volume Serial Number is 0E33-300C

 Directory of C:\src\t

2020-07-06  14:25                20 yy-hlink.txt
2020-07-06  14:23    <SYMLINK>      yy-slink.txt [C:\src\t\yy.txt]
2020-07-06  14:24                20 yy.txt
               3 File(s)             40 bytes
               0 Dir(s)  739,939,672,064 bytes free

Configuration

C:>dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.100-preview.5.20279.10
 Commit:    8139f1b74e

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18363
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Users\pwatson\AppData\Local\Microsoft\dotnet\sdk\5.0.100-preview.5.20279.10\

Host (useful for support):
  Version: 5.0.0-preview.5.20278.1
  Commit:  4ae4e2fe08

.NET SDKs installed:
  2.2.402 [C:\Program Files\dotnet\sdk]
  3.0.100-rc1-014190 [C:\Program Files\dotnet\sdk]
  3.1.301 [C:\Program Files\dotnet\sdk]
  5.0.100-preview.5.20279.10 [C:\Users\pwatson\AppData\Local\Microsoft\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.0-rc1.19457.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.0-preview.5.20279.2 [C:\Users\pwatson\AppData\Local\Microsoft\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0-rc1-19456-20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.0-preview.5.20278.1 [C:\Users\pwatson\AppData\Local\Microsoft\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0-rc1-19456-20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.0-preview.5.20278.3 [C:\Users\pwatson\AppData\Local\Microsoft\dotnet\shared\Microsoft.WindowsDesktop.App]

Regression?

Unknown

Other information

PS C:\src\t> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.0.1
PSEdition                      Core
GitCommitId                    7.0.1
OS                             Microsoft Windows 10.0.18363
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[Dotnet-GitSync-Bot]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[NikolaMilosavljevic]

@jeffschwMSFT this doesn't seem related to Setup, can you reassign to FileSystem owners?

[mklement0]

@Liturgist, allow me to provide a more succinct repro:

Run either in PowerShell [Core] v6+ or in Windows PowerShell, in which case the session must be elevated:

# Create a test target file.
$null > tmp.txt

# Create a symlink to it.
$link = New-Item -Force -ItemType SymbolicLink tmpL.txt -Target tmp.txt

# Try to modify the *symlink*'s LastWriteTime.
$link.LastWriteTime = '2020-01-01'

# List both the link and the target, which shows that the *target*'s
# LastWriteTime was modified.
Get-Item tmp.txt, tmpL.txt -OutVariable result

# Clean up.
$result | Remove-Item

In PowerShell Core, you'll get output such as the following, showing that the target was modified, not the link itself:

    Directory: /Users/jdoe

UnixMode   User             Group                 LastWriteTime           Size Name
--------   ----             -----                 -------------           ---- ----
-rw-r--r-- mklement         staff                1/1/2020 00:00              0 tmp.txt
lrwxr-xr-x mklement         staff                8/6/2020 13:42              7 tmpL.txt -> /Users/jdoe/tmp.txt

See also: The proposed symlink API in #24271

[carlossanlop]

Thanks for the details.

I know in Linux, there are ways to manipulate the attributes of the symbolic link itself, For example you can read the file attributes using stat and you can read the symbolic link attributes using lstat. You can also use touch to alter the timestamp of a file, and you can use touch -h to alter the timestamp of the symbolic link itself.

What I would like to investigate is if Windows has similar options to modify symbolic link attributes. I know the Windows methods to create symbolic links, but I can't find a method to edit an existing symbolic link.

@Liturgist can you share more information about why you want to edit the symbolic link attributes, and specifically, the timestamps?

[hamarb123]

@carlossanlop I've implemented fixes for this in #49555.
I'm happy to make another PR for Windows as per #49555 (comment) with the changes that I removed in a617a01. These changes make it set on the symlink and they pass my additional test (SettingUpdatesPropertiesOnSymlink in BaseGetSetTimes.cs currently in PR #49555).
I'm happy to be assigned to this issue.

[carlossanlop]

Thank you so much for offering your help, @hamarb123 ! I assigned this issue to you per your request. I'm looking forward to reviewing your PR.