Manpages - fileno.3

fileno - obtain file descriptor of a stdio stream

  #include <stdio.h>

  int fileno(FILE *stream);

Feature Test Macro Requirements for glibc (see *feature_test_macros*(7)):

*fileno*():

      _POSIX_C_SOURCE

The function *fileno*() examines the argument stream and returns the integer file descriptor used to implement this stream. The file descriptor is still owned by stream and will be closed when *fclose*(3) is called. Duplicate the file descriptor with *dup*(2) before passing it to code that might close it.

For the nonlocking counterpart, see *unlocked_stdio*(3).

On success, *fileno*() returns the file descriptor associated with stream. On failure, -1 is returned and errno is set to indicate the error.

EBADF

stream is not associated with a file.

For an explanation of the terms used in this section, see *attributes*(7).

The function *fileno*() conforms to POSIX.1-2001 and POSIX.1-2008.

*open*(2), *fdopen*(3), *stdio*(3), *unlocked_stdio*(3)

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