FreeBSD manual
download PDF document: fdown.3.pdf
FDOWN(3) Schily's LIBRARY FUNCTIONS FDOWN(3)
NAME
fdown() - returns a logical unit number
SYNOPSIS
int fdown(f)
FILE *f;
DESCRIPTION
fdown(), given a standard I/O FILE *f, returns the file number. A file
number is usually a small number like 2 which is not a unique number
system-wide but is peculiar to the specified process. fdown() can be
used to implement additional functions not provided for in the standard
I/O library. It verifies that the file was opened via fileopen().
RETURNS
Returns the actual system file number.
NOTES
Since this call is system dependent, it should be used carefully.
Joerg Schilling 2022/09/09 FDOWN(3)