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FileLocked

Function FileLocked( const aFilePath : string) : boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := FileLocked('C:\Fictional\Inbound\order.xml');
end;

Usage​

FileLocked reports whether Velox cannot open a path for read/write access while denying other writers.

Parameters

NameTypeDescription
aFilePathstring, constLiteral file path to probe. Wildcards are not expanded by Velox open.

Returns

False when FileOpen(aFilePath, fmOpenReadWrite or fmShareDenyWrite) returns a valid handle; otherwise True.

Behaviour

  • A compatible existing writable file normally returns False.
  • A file held with an incompatible sharing mode returns True.
  • The probe itself briefly prevents other writers while its handle is open.
  • No handle or lock remains after return.

Important usage notes

  • True does not specifically prove another process holds a lock. Missing files, read-only media/attributes, denied permissions, directories, invalid paths and unavailable shares also fail the requested read/write open.
  • A file can be readable but still report True because write access is requested.
  • A current compatible open does not guarantee the next open; another actor can change sharing or delete/replace the path immediately.
  • Relative paths depend on shared across the Velox process current-directory state.

Errors

All ordinary open errors are collapsed to True; no last-error code or exception is exposed.

Additional Technical Info​

FileLocked returns False only when Velox can briefly open the path for both reading and writing while allowing other readers but denying other writers. Every open failure is reported as True.

The example is source-reviewed and was not executed by the documentation workflow.

Implementation

Installed Delphi FileOpen maps this mode to Win32 CreateFileW with GENERIC_READ or GENERIC_WRITE, share mode FILE_SHARE_READ, OPEN_EXISTING and FILE_ATTRIBUTE_NORMAL. Velox closes a successful handle immediately.

Side effects

Opens and closes the file on success. It does not modify file content, but the temporary share mode can briefly affect competing opens.

Performance and concurrency

One synchronous open/close probe. Network paths can block. The result is a momentary observation, not a durable concurrency primitive.

Remarks

Interpret the result as “not openable with this exact mode.” Handle the real open/write operation's result even after False.

Related entries

External references

Created 2026-07-15