Synopsis

#include <stdio.h>

FILE *fdopen(int fildes, const char *mode);

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

The fdopen() function shall associate a stream with a file descriptor.

The mode argument is a character string having one of the following values:

  • r or rb - Open a file for reading.
  • w or wb - Open a file for writing.
  • a or ab - Open a file for writing at end-of-file.
  • r+ or rb+ or r+b - Open a file for update (reading and writing).
  • w+ or wb+ or w+b - Open a file for update (reading and writing).
  • a+ or ab+ or a+b - Open a file for update (reading and writing) at end-of-file.

The meaning of these flags is exactly as specified in fopen(), except that modes beginning with w shall not cause truncation of the file.

Additional values for the mode argument may be supported by an implementation.

The application shall ensure that the mode of the stream as expressed by the mode argument is allowed by the file access mode of the open file description to which fildes refers. The file position indicator associated with the new stream is set to the position indicated by the file offset associated with the file descriptor.

The error and end-of-file indicators for the stream shall be cleared. The fdopen() function may cause the last data access timestamp of the underlying file to be marked for update.

If fildes refers to a shared memory object, the result of the fdopen() function is unspecified.

If fildes refers to a typed memory object, the result of the fdopen() function is unspecified. The fdopen() function shall preserve the offset maximum previously set for the open file description corresponding to fildes.

Return value

Upon successful completion, fdopen() shall return a pointer to a stream, otherwise, a null pointer shall be returned and errno set to indicate the error.

Errors

The fdopen() function shall fail if:

  • EMFILE - STREAM_MAX streams are currently open in the calling process.

The fdopen() function may fail if:

  • EBADF - The fildes argument is not a valid file descriptor.

  • EINVAL - The mode argument is not a valid mode.

  • EMFILE - FOPEN_MAX streams are currently open in the calling process.

  • ENOMEM - Insufficient space to allocate a buffer.

Tests

Untested

Known bugs

None

See Also

  1. Standard library functions
  2. Table of Contents