dosseek

Purpose

     Moves the DOS file read/write pointer.

Library

     DOS Services Library (libdos.a)

Syntax

     #include <dos.h>

     int dosseek (dosfile, offset, whence)
     DOSFILE dosfile;
     long offset;
     int whence;

Description

     The dosseek subroutine moves the current position pointer
     in the file specified by the dosfile parameter.

     o   If the whence  parameter is 0, the pointer  is set to
         the position specified by the offset parameter.

     o   If the whence  parameter is 1, the  pointer is incre-
         mented by the number of bytes specified by the offset
         parameter.

     o   If the whence  parameter is 2, the pointer  is set to
         the size of the file  plus the number of bytes speci-
         fied by the offset parameter.

     If the dosseek subroutine has  been issued on a file that
     was opened with the DO_ASCII  flag set, the offset param-
     eter must  be 0.   Otherwise, the results  are unpredict-
     able.

Return Value

     Upon  successful completion,  the file  pointer value  is
     returned.  If the dosseek subroutine fails, a value of -1
     is returned and doserrno is set to indicate the error.

Diagnostics

     The dosseek subroutine fails and the file pointer remains
     unchanged if one or more of the following are true:

     EBADF      dosfile is not an open file descriptor.

     ESPIPE     dosfile is associated with a pipe or FIFO.

     EINVAL     whence is not  0, 1 or 2.  This  also causes a
                SIGSYS signal.

     EINVAL     The resulting file pointer would be negative.

Related Information

     In  this  book:   "DOS services  library,"  "doscreate,"
     "dosdup," and "dosopen."