Lahey/GNU Fortran

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8.92 FSEEK — Low level file positioning subroutine

Description:
Moves UNIT to the specified OFFSET. If WHENCE is set to 0, the OFFSET is taken as an absolute value SEEK_SET, if set to 1, OFFSET is taken to be relative to the current position SEEK_CUR, and if set to 2 relative to the end of the file SEEK_END. On error, STATUS is set to a nonzero value. If STATUS the seek fails silently.

This intrinsic routine is not fully backwards compatible with g77. In g77, the FSEEK takes a statement label instead of a STATUS variable. If FSEEK is used in old code, change

            CALL FSEEK(UNIT, OFFSET, WHENCE, *label)
     

to

            INTEGER :: status
            CALL FSEEK(UNIT, OFFSET, WHENCE, status)
            IF (status /= 0) GOTO label
     

Please note that GNU Fortran provides the Fortran 2003 Stream facility. Programmers should consider the use of new stream IO feature in new code for future portability. See also Fortran 2003 status.

Standard:
GNU extension
Class:
Subroutine
Syntax:
CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])
Arguments:

UNIT Shall be a scalar of type INTEGER.
OFFSET Shall be a scalar of type INTEGER.
WHENCE Shall be a scalar of type INTEGER. Its value shall be either 0, 1 or 2.
STATUS (Optional) shall be a scalar of type INTEGER(4).

Example:
          PROGRAM test_fseek
            INTEGER, PARAMETER :: SEEK_SET = 0, SEEK_CUR = 1, SEEK_END = 2
            INTEGER :: fd, offset, ierr
          
            ierr   = 0
            offset = 5
            fd     = 10
          
            OPEN(UNIT=fd, FILE="fseek.test")
            CALL FSEEK(fd, offset, SEEK_SET, ierr)  ! move to OFFSET
            print *, FTELL(fd), ierr
          
            CALL FSEEK(fd, 0, SEEK_END, ierr)       ! move to end
            print *, FTELL(fd), ierr
          
            CALL FSEEK(fd, 0, SEEK_SET, ierr)       ! move to beginning
            print *, FTELL(fd), ierr
          
            CLOSE(UNIT=fd)
          END PROGRAM
     

See also:
FTELL