2.11BSD#431 - /usr/man/cat3f/twrite.0

TOPEN(3F)	    UNIX Programmer's Manual		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'', tlu, is
     ``topen''ed in much the same way as a normal f77 logical
     unit is ``open''ed.  All other operations are performed via
     the tlu.  The tlu has no relationship at all to any normal
     f77 logical unit.

     Topen associates a device name with a tlu.  Tlu must be in
     the range 0 to 3.	The logical argument label should indi-
     cate whether the tape includes a tape label.  This is used
     by trewin below.  Topen does not move the tape.  The normal
     returned value is 0.  If the value of the function is nega-
     tive, an error has occured.  See perror(3F) for details.

     Tclose closes the tape device channel and removes its asso-
     ciation with tlu.	The normal returned value is 0.  A nega-
     tive value indicates an error.


Printed 11/26/99	  May 15, 1985				1


TOPEN(3F)	    UNIX Programmer's Manual		TOPEN(3F)


     Tread reads the next physical record from tape to buffer.
     Buffer must be of type character.	The size of buffer 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.

     Twrite writes a physical record to tape from buffer.  The
     physical record length will be the size of buffer.  Buffer
     must be of type character.  The number of bytes written will
     be returned.  A value of 0 or negative indicates an error.

     Trewin rewinds the tape associated with tlu to the beginning
     of the first data file.  If the tape is a labelled tape (see
     topen above) then the label is skipped over after rewinding.
     The normal returned value is 0.  A negative value indicates
     an error.

     Tskipf allows the user to skip over files and/or records.
     First, nfiles 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 tlu.) Next, nrecs
     physical records are skipped over.  The normal returned
     value is 0.  A negative value indicates an error.

     Finally, tstate allows the user to determine the logical
     state of the tape I/O channel and to see the tape drive con-
     trol status register.  The values of fileno and recno will
     be returned and indicate the current file and record number.
     The logical values errf, eoff, and eotf 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 tcsr will reflect the tape drive con-
     trol status register.  See ht(4) for details.

FILES
     /usr/lib/libU77.a

SEE ALSO
     ht(4), perror(3F), rewind(1)


Printed 11/26/99	  May 15, 1985				2