PKOPEN(3)           UNIX Programmer's Manual            PKOPEN(3)

NAME
     pkopen, pkclose, pkread, pkwrite, pkfail - packet driver
     simulator

SYNOPSIS
     char *pkopen(fd)

     pkclose(ptr)
     char *ptr;

     pkread(ptr, buffer, count)
     char *ptr, *buffer;

     pkwrite(ptr, buffer, count)
     char *ptr, *buffer;

     pkfail()

DESCRIPTION
     These routines are a user-level implementation of the full-
     duplex end-to-end communication protocol described in _p_k(4).
     If _f_d is a file descriptor open for reading and writing,
     _p_k_o_p_e_n carries out the initial synchronization and returns
     an identifying pointer.  The pointer is used as the first
     parameter to _p_k_r_e_a_d, _p_k_w_r_i_t_e, and _p_k_c_l_o_s_e.

     _P_k_r_e_a_d, _p_k_w_r_i_t_e and _p_k_c_l_o_s_e behave analogously to _r_e_a_d,
     _w_r_i_t_e and _c_l_o_s_e(2).  However, a write of zero bytes is mean-
     ingful and will produce a corresponding read of zero bytes.

SEE ALSO
     pkon(2), pk(4)

DIAGNOSTICS
     _P_k_f_a_i_l is called upon persistent breakdown of communication.
     _P_k_f_a_i_l must be supplied by the user.

     _P_k_o_p_e_n returns a null (0) pointer if packet protocol can not
     be established.

     _P_k_r_e_a_d returns -1 on end of file, 0 in correspondence with a
     0-length write.

BUGS
     This simulation of _p_k(4) leaves something to be desired in
     needing special read and write routines, and in not being
     inheritable across calls of _e_x_e_c_v_e(2).  Its prime use is on
     systems that lack _p_k.
     These functions use _a_l_a_r_m(2); simultaneous use of _a_l_a_r_m for
     other puposes may cause trouble.

Printed 7/31/83                                                 1