fileno.3: Split fileno(3) content out of ferror(3) into new page

fileno(3) differs from the other functions in various ways.
For example, it is governed by different standards,
and can set 'errno'. Conversely, the other functions
are about examining the status of a stream, while
fileno(3) simply obtains the underlying file descriptor.
Furthermore, splitting this function out allows
for some cleaner upcoming changes in ferror(3).

Signed-off-by: Michael Kerrisk <>
1 file changed