One more thing...

src/libraries/System.Private.CoreLib/src/System/Environment.Unix.cs

@@ -74,5 +74,41 @@ public static unsafe string UserName
 
  }
  }
+
+ private static unsafe bool TryGetUserNameFromPasswd(byte* buf, int bufLen, out string? username)
+ {
+ // Call getpwuid_r to get the passwd struct
+ Interop.Sys.Passwd passwd;
+ int error = Interop.Sys.GetPwUidR(Interop.Sys.GetEUid(), out passwd, buf, bufLen);
+
+ // If the call succeeds, give back the user name retrieved
+ if (error == 0)
+ {
+ Debug.Assert(passwd.Name != null);
+ username = Marshal.PtrToStringAnsi((IntPtr)passwd.Name);
+ return true;
+ }
+
+ // If the current user's entry could not be found, give back null,
+ // but still return true (false indicates the buffer was too small).
+ if (error == -1)
+ {
+ username = null;
+ return true;
+ }
+
+ var errorInfo = new Interop.ErrorInfo(error);
+
+ // If the call failed because the buffer was too small, return false to
+ // indicate the caller should try again with a larger buffer.
+ if (errorInfo.Error == Interop.Error.ERANGE)
+ {
+ username = null;
+ return false;
+ }
+
+ // Otherwise, fail.
+ throw new IOException(errorInfo.GetErrorMessage(), errorInfo.RawErrno);
+ }
  }
 }

src/libraries/System.Private.CoreLib/src/System/Environment.UnixOrBrowser.cs

@@ -56,42 +56,6 @@ private static string ExpandEnvironmentVariablesCore(string name)
 
  public static int SystemPageSize => CheckedSysConf(Interop.Sys.SysConfName._SC_PAGESIZE);
 
- private static unsafe bool TryGetUserNameFromPasswd(byte* buf, int bufLen, out string? username)
- {
- // Call getpwuid_r to get the passwd struct
- Interop.Sys.Passwd passwd;
- int error = Interop.Sys.GetPwUidR(Interop.Sys.GetEUid(), out passwd, buf, bufLen);
-
- // If the call succeeds, give back the user name retrieved
- if (error == 0)
- {
- Debug.Assert(passwd.Name != null);
- username = Marshal.PtrToStringAnsi((IntPtr)passwd.Name);
- return true;
- }
-
- // If the current user's entry could not be found, give back null,
- // but still return true (false indicates the buffer was too small).
- if (error == -1)
- {
- username = null;
- return true;
- }
-
- var errorInfo = new Interop.ErrorInfo(error);
-
- // If the call failed because the buffer was too small, return false to
- // indicate the caller should try again with a larger buffer.
- if (errorInfo.Error == Interop.Error.ERANGE)
- {
- username = null;
- return false;
- }
-
- // Otherwise, fail.
- throw new IOException(errorInfo.GetErrorMessage(), errorInfo.RawErrno);
- }
-
  public static string UserDomainName => MachineName;
 
  /// <summary>Invoke <see cref="Interop.Sys.SysConf"/>, throwing if it fails.</summary>