osx man page for getdtablesize

GETDTABLESIZE(2)					      BSD System Calls Manual						  GETDTABLESIZE(2)

NAME
     getdtablesize -- get descriptor table size

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     getdtablesize(void);

DESCRIPTION
     Each process has a fixed size descriptor table, which is guaranteed to have at least 20 slots.  The entries in the descriptor table are num-
     bered with small integers starting at 0.  The call getdtablesize() returns the size of this table.

LEGACY
     The getrlimit(2) function returns a value of type rlim_t.	This interface, returning an int, may have problems representing appropriate val-
     ues in the future.  Applications should use the getrlimit(2) function instead.

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

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

BSD
								   June 4, 1993 							       BSD