diff options
Diffstat (limited to 'gcc/fortran/intrinsic.texi')
| -rw-r--r-- | gcc/fortran/intrinsic.texi | 64 |
1 files changed, 58 insertions, 6 deletions
diff --git a/gcc/fortran/intrinsic.texi b/gcc/fortran/intrinsic.texi index b71609b4dd4..4e6b26a21d9 100644 --- a/gcc/fortran/intrinsic.texi +++ b/gcc/fortran/intrinsic.texi @@ -3966,10 +3966,31 @@ See @code{MALLOC} for an example. @cindex file operation, seek @cindex file operation, position -Not yet implemented in GNU Fortran. - @table @asis @item @emph{Description}: +Moves @var{UNIT} to the specified @var{OFFSET}. If @var{WHENCE} +is set to 0, the @var{OFFSET} is taken as an absolute value @code{SEEK_SET}, +if set to 1, @var{OFFSET} is taken to be relative to the current position +@code{SEEK_CUR}, and if set to 2 relative to the end of the file @code{SEEK_END}. +On error, @var{STATUS} is set to a non-zero value. If @var{STATUS} the seek +fails silently. + +This intrinsic routine is not fully backwards compatible with @command{g77}. +In @command{g77}, the @code{FSEEK} takes a statement label instead of a +@var{STATUS} variable. If FSEEK is used in old code, change +@smallexample + CALL FSEEK(UNIT, OFFSET, WHENCE, *label) +@end smallexample +to +@smallexample + INTEGER :: status + CALL FSEEK(UNIT, OFFSET, WHENCE, status) + IF (status /= 0) GOTO label +@end smallexample + +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 @ref{Fortran 2003 status}. @item @emph{Standard}: GNU extension @@ -3978,13 +3999,44 @@ GNU extension Subroutine @item @emph{Syntax}: +@code{CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])} + @item @emph{Arguments}: -@item @emph{Return value}: +@multitable @columnfractions .15 .70 +@item @var{UNIT} @tab Shall be a scalar of type @code{INTEGER}. +@item @var{OFFSET} @tab Shall be a scalar of type @code{INTEGER}. +@item @var{WHENCE} @tab Shall be a scalar of type @code{INTEGER}. +Its value shall be either 0, 1 or 2. +@item @var{STATUS} @tab (Optional) shall be a scalar of type +@code{INTEGER(4)}. +@end multitable + @item @emph{Example}: -@item @emph{Specific names}: -@item @emph{See also}: -@uref{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19292, g77 features lacking in gfortran} +@smallexample +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 +@end smallexample + +@item @emph{See also}: +@ref{FTELL} @end table |