fd_close()

Close an open file descriptor.

Description

The fd_close() function is used to close an open file descriptor. For sockets, this function will flush the data before closing the socket.

Syntax

  ;;; Note: This is similar to `close` in POSIX.
  ;;; Close a file descriptor.
  (@interface func (export "fd_close")
    (param $fd $fd)
    (result $error (expected (error $errno)))
  )

Parameters

• ctx: A mutable reference to the function environment.
• fd: The file descriptor mapping to an open file to close.

Return Value

The function returns a Result containing an Errno value indicating the success or failure of the operation. An Errno::Success value indicates a successful closure.

Errors

The function can return the following errors:

• Errno::Isdir: If the provided fd corresponds to a directory.
• Errno::Badf: If the provided fd is invalid or not open.

Logging

This function has been instrumented with debug-level logging. It will log the following information:

• pid: The process ID of the current execution context.
• %fd: The file descriptor being closed.
• err: Any encountered error during the closing process.

Note

The fd_close() function is used to close an open file descriptor. It releases any resources associated with the file descriptor. For sockets, it is best practise to run sock_shutdown() before closing, because otherwise it can have unexpected runtime and latency side affects in some wasm runtimes.