TOPEN(3F) TOPEN(3F) NAME topen, tclose, tread, twrite, trewin, tskipf, tstate - f77 tape I/O SYNOPSIS integer function topen (tlu, devnam, label) integer tlu character*(*) devnam logical label integer function tclose (tlu) integer tlu integer function tread (tlu, buffer) integer tlu character*(*) buffer integer function twrite (tlu, buffer) integer tlu character*(*) buffer integer function trewin (tlu) integer tlu integer function tskipf (tlu, nfiles, nrecs) integer tlu, nfiles, nrecs integer function tstate (tlu, fileno, recno, errf, eoff, eotf, tcsr) integer tlu, fileno, recno, tcsr logical errf, eoff, eotf DESCRIPTION These functions provide a simple interface between f77 and magnetic tape devices. A ‘‘tape logical unit’’, _t_l_u, is ‘‘topen’’ed in much the same way as a normal f77 logical unit is ‘‘open’’ed. All other opera‐ tions are performed via the _t_l_u. The _t_l_u has no relationship at all to any normal f77 logical unit. _T_o_p_e_n associates a device name with a _t_l_u. _T_l_u must be in the range 0 to 3. The logical argument _l_a_b_e_l should indicate whether the tape includes a tape label. This is used by _t_r_e_w_i_n below. _T_o_p_e_n does not move the tape. The normal returned value is 0. If the value of the function is negative, an error has occured. See _p_e_r_r_o_r(3F) for details. _T_c_l_o_s_e closes the tape device channel and removes its association with _t_l_u. The normal returned value is 0. A negative value indicates an error. _T_r_e_a_d reads the next physical record from tape to _b_u_f_f_e_r. _B_u_f_f_e_r must be of type character. The size of _b_u_f_f_e_r should be large enough to hold the largest physical record to be read. The actual number of bytes read will be returned as the value of the function. If the value is 0, the end-of-file has been detected. A negative value indicates an error. _T_w_r_i_t_e writes a physical record to tape from _b_u_f_f_e_r. The physical record length will be the size of _b_u_f_f_e_r. _B_u_f_f_e_r must be of type char‐‐ acter. The number of bytes written will be returned. A value of 0 or negative indicates an error. _T_r_e_w_i_n rewinds the tape associated with _t_l_u to the beginning of the first data file. If the tape is a labelled tape (see _t_o_p_e_n above) then the label is skipped over after rewinding. The normal returned value is 0. A negative value indicates an error. _T_s_k_i_p_f allows the user to skip over files and/or records. First, _n_f_i_l_e_s end-of-file marks are skipped. If the current file is at EOF, this counts as 1 file to skip. (Note: This is the way to reset the EOF status for a _t_l_u.) Next, _n_r_e_c_s physical records are skipped over. The normal returned value is 0. A negative value indicates an error. Finally, _t_s_t_a_t_e allows the user to determine the logical state of the tape I/O channel and to see the tape drive control status register. The values of _f_i_l_e_n_o and _r_e_c_n_o will be returned and indicate the cur‐ rent file and record number. The logical values _e_r_r_f, _e_o_f_f, and _e_o_t_f indicate an error has occurred, the current file is at EOF, or the tape has reached logical end-of-tape. End-of-tape (EOT) is indicated by an empty file, often referred to as a double EOF mark. It is not allowed to read past EOT although it is allowed to write. The value of _t_c_s_r will reflect the tape drive control status register. See _h_t(4) for details. FILES /usr/lib/libU77.a SEE ALSO ht(4), perror(3F), rewind(1) 4.2 Berkeley Distribution May 15, 1985 TOPEN(3F)