1FUNOPEN(3) 386BSD Programmer's Manual FUNOPEN(3) 2 3NNAAMMEE 4 ffuunnooppeenn, ffrrooppeenn, ffwwooppeenn - open a stream 5 6SSYYNNOOPPSSIISS 7 ##iinncclluuddee <<ssttddiioo..hh>> 8 9 _F_I_L_E * 10 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), 11 _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), 12 _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 *)) 13 14 _F_I_L_E * 15 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)) 16 17 _F_I_L_E * 18 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)) 19 20DDEESSCCRRIIPPTTIIOONN 21 The ffuunnooppeenn() function associates a stream with up to four ``I/O 22 functions''. Either _r_e_a_d_f_n or _w_r_i_t_e_f_n must be specified; the others can 23 be given as an appropriately-typed NULL pointer. These I/O functions 24 will be used to read, write, seek and close the new stream. 25 26 In general, omitting a function means that any attempt to perform the 27 associated operation on the resulting stream will fail. If the close 28 function is omitted, closing the stream will flush any buffered output 29 and then succeed. 30 31 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 32 those, respectively, of read(2), write(2), seek(2), and close(2) with 33 the single exception that they are passed the _c_o_o_k_i_e argument specified 34 to ffuunnooppeenn() in place of the traditional file descriptor argument. 35 36 Read and write I/O functions are allowed to change the underlying buffer 37 on fully buffered or line buffered streams by calling setvbuf(3). They 38 are also not required to completely fill or empty the buffer. They are 39 not, however, allowed to change streams from unbuffered to buffered or to 40 change the state of the line buffering flag. They must also be prepared 41 to have read or write calls occur on buffers other than the one most 42 recently specified. 43 44 All user I/O functions can report an error by returning -1. 45 Additionally, all of the functions should set the external variable _e_r_r_n_o 46 appropriately if an error occurs. 47 48 An error on cclloosseeffnn() does not keep the stream open. 49 50 As a convenience, the include file <_s_t_d_i_o._h> defines the macros ffrrooppeenn() 51 and ffwwooppeenn() as calls to ffuunnooppeenn() with only a read or write function 52 specified. 53 54RREETTUURRNN VVAALLUUEESS 55 Upon successful completion, ffuunnooppeenn() returns a FILE pointer. Otherwise, 56 NULL is returned and the global variable _e_r_r_n_o is set to indicate the 57 error. 58 59EERRRROORRSS 60 [EINVAL] The ffuunnooppeenn() function was called without either a read or 61 write function. The ffuunnooppeenn() function may also fail and set 62 _e_r_r_n_o for any of the errors specified for the routine 63 malloc(3). 64 65SSEEEE AALLSSOO 66 fcntl(2), open(2), fclose(3), fopen(3), fseek(3), setbuf(3) 67 68HHIISSTTOORRYY 69 These functions are currently under development. 70 71BBUUGGSS 72 The ffuunnooppeenn() function may not be portable to systems other than BSD 73 UNIX. 74 75BSD Experimental April 19, 1991 2 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133