ErrnoException

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Base class for exceptions reported via the C errno variable

Subclasses exist for some specific Errno values, such as:

• ChildProcessException (ECHILD)
• ConnectionException and its' subclasses, BrokenPipeException (EPIPE, ESHUTDOWN), ConnectionAbortedException (ECONNABORTED), ConnectionRefusedException (ECONNREFUSED), and ConnectionResetException (ECONNRESET)
• AlreadyExistsException (EEXIST)
• NotFoundException (ENOENT)
• IsADirectoryException (EISDIR)
• IsNotADirectoryException (ENOTDIR)
• PermissionException (EACCESS, EPERM)
• ProcessLookupException (ESRCH)
• TimeoutError (ETIMEDOUT)

It is strongly recommended to catch subclasses instead of this class if a suitable subclass is defined; for example:

// ANTIPATTERN:
catch (OS\ErrnoException $e) {
  if ($e->getErrno() === OS\Errno::ENOENT) {
    do_stuff();
  }
}
// RECOMMENDED:
catch (OS\NotFoundException $_) {
  do_stuff();
}

If a suitable subclass is not defined, the antipattern is unavoidable.

Interface Synopsis

namespace HH\Lib\OS;

class ErrnoException extends \Exception {...}

Public Methods

• ->__construct(Errno $errno, string $message)
• ->getCode(): Errno
  Deprecated for clarity, and potential future ambiguity
• ->getErrno(): Errno