4.4BSD/usr/share/man/cat3/funopen.0

FUNOPEN(3)                  BSD Programmer's Manual                 FUNOPEN(3)

NNAAMMEE
     ffuunnooppeenn, ffrrooppeenn, ffwwooppeenn - open a stream

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<ssttddiioo..hh>>

     _F_I_L_E _*
     ffuunnooppeenn(_v_o_i_d _*_c_o_o_k_i_e, _i_n_t _(_*_r_e_a_d_f_n_)_(_v_o_i_d _*_, _c_h_a_r _*_, _i_n_t_),
             _i_n_t _(_w_r_i_t_e_f_n_*_)_(_v_o_i_d _*_, _c_o_n_s_t _c_h_a_r _*_, _i_n_t_),
             _f_p_o_s___t _(_s_e_e_k_f_n_*_)_(_v_o_i_d _*_, _f_p_o_s___t_, _i_n_t_), _i_n_t _(_c_l_o_s_e_f_n_*_)_(_v_o_i_d _*_));

     _F_I_L_E _*
     ffrrooppeenn(_v_o_i_d _*_c_o_o_k_i_e, _i_n_t _(_*_r_e_a_d_f_n_)_(_v_o_i_d _*_, _c_h_a_r _*_, _i_n_t_));

     _F_I_L_E _*
     ffwwooppeenn(_v_o_i_d _*_c_o_o_k_i_e, _i_n_t _(_*_w_r_i_t_e_f_n_)_(_v_o_i_d _*_, _c_h_a_r _*_, _i_n_t_));

DDEESSCCRRIIPPTTIIOONN
     The ffuunnooppeenn() function associates a stream with up to four ``I/O
     functions''. Either _r_e_a_d_f_n or _w_r_i_t_e_f_n must be specified; the others can
     be given as an appropriately-typed NULL pointer.  These I/O functions
     will be used to read, write, seek and close the new stream.

     In general, omitting a function means that any attempt to perform the as-
     sociated operation on the resulting stream will fail.  If the close func-
     tion is omitted, closing the stream will flush any buffered output and
     then succeed.

     The calling conventions of _r_e_a_d_f_n, _w_r_i_t_e_f_n, _s_e_e_k_f_n and _c_l_o_s_e_f_n must match
     those, respectively, of read(2),  write(2),  seek(2),  and close(2) with
     the single exception that they are passed the _c_o_o_k_i_e argument specified
     to ffuunnooppeenn() in place of the traditional file descriptor argument.

     Read and write I/O functions are allowed to change the underlying buffer
     on fully buffered or line buffered streams by calling setvbuf(3).  They
     are also not required to completely fill or empty the buffer.  They are
     not, however, allowed to change streams from unbuffered to buffered or to
     change the state of the line buffering flag.  They must also be prepared
     to have read or write calls occur on buffers other than the one most re-
     cently specified.

     All user I/O functions can report an error by returning -1.  Additional-
     ly, all of the functions should set the external variable _e_r_r_n_o appropri-
     ately if an error occurs.

     An error on cclloosseeffnn() does not keep the stream open.

     As a convenience, the include file <_s_t_d_i_o_._h> defines the macros ffrrooppeenn()
     and ffwwooppeenn() as calls to ffuunnooppeenn() with only a read or write function
     specified.

RREETTUURRNN VVAALLUUEESS
     Upon successful completion, ffuunnooppeenn() returns a FILE pointer.  Otherwise,
     NULL is returned and the global variable _e_r_r_n_o is set to indicate the er-
     ror.

EERRRROORRSS
     [EINVAL]  The ffuunnooppeenn() function was called without either a read or
               write function.  The ffuunnooppeenn() function may also fail and set
               _e_r_r_n_o for any of the errors specified for the routine
               malloc(3).

SSEEEE AALLSSOO
     fcntl(2),  open(2),  fclose(3),  fopen(3),  fseek(3),  setbuf(3)

HHIISSTTOORRYY
     The ffuunnooppeenn() functions first appeared in 4.4BSD.

BBUUGGSS
     The ffuunnooppeenn() function may not be portable to systems other than BSD.

4.4BSD                           June 9, 1993                                2