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9.116 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 — Current stream position