netbsd man page for getdtablesize

GETDTABLESIZE(3)					   BSD Library Functions Manual 					  GETDTABLESIZE(3)

NAME
     getdtablesize -- get descriptor table size

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     getdtablesize(void);

DESCRIPTION
     The getdtablesize function is an equivalent of sysconf() with _SC_OPEN_MAX.

SEE ALSO
     close(2), dup(2), getrlimit(2), open(2), select(2), sysconf(3)

HISTORY
     The getdtablesize() function call appeared in 4.2BSD.

     Historically, each process had a fixed size descriptor table, which is guaranteed to have at least 20 slots.  The entries in the descriptor
     table are numbered with small integers starting at 0.  The call getdtablesize() used to return the size of this table.  It doesn't make much
     sense these days because the size of the table is dynamic.

BSD
								  January 5, 2012							       BSD