Manual Reference Pages - flush (7fortran)
NAME
flush(7f) - [IO] flush I/O buffers of specified files
SYNOPSIS
flush file-unit-number flush([UNIT=]file_unit_number,[iostat=i],[iomsg=str],[err=label_number])
DESCRIPTION
I/O statements can buffer output before delivering it to the host system in order to minimize the overhead of system calls. Use FLUSH(7F) to deliver any such pending I/O for the identified file to the host system.
This is generally not required accept to ensure critical information is displayed or written as reliably as possible or to synchronise data from different units going to the same device. Do not arbitrarily flush all I/O operations or programs using large amounts of I/O might experience significant performance degradation, particularly if the I/O is to a block-oriented device.
Note execution of a FLUSH(7F) statement performs a wait operation for all pending asynchronous data transfer operations for the specified unit.
More generally execution of a FLUSH(7F) statement causes data written to an external file not only to be available to other processes, causes data placed in an external file by means other than Fortran to be available to a READ(7F) statement; but these actions are processor dependent.
Execution of a FLUSH(7F) statement for a file that is connected but does not exist is permitted and has no effect on any file.
A FLUSH(7F) statement has no effect on file position.
OPTIONS
UNIT A file-unit-number is required; if the optional characters "UNIT=" are omitted, the unit-number must be the first item in the FLUSH(7) statement.
RETURNS
IOSTAT : status variable. It is set to a processor-dependent positive value if an error occurs, to zero if the flush operation was successful, or to a processor-dependent negative value if the flush operation is not supported for the unit specified. IOMSG : character variable holding error description when iostat is not zero. ERR : The numeric line label of a target statement in the same scope as the FLUSH(7F) statement.
NOTE From the Fortran standard:
Because the Fortran standard does not specify the mechanism of file storage, the exact meaning of the flush operation is not precisely defined. It is expected that the flush operation will make all data written to a file available to other processes or devices, or make data recently added to a file by other processes or devices available to the program via a subsequent read operation. This is commonly called flushing input/output buffers.
EXAMPLES
Sample program:
program demo_flush use, intrinsic :: iso_fortran_env, only : & & stderr=>ERROR_UNIT, & & stdin=>INPUT_UNIT, & & stdout=>OUTPUT_UNIT implicit none integer :: iostat character(len=255) :: iomsg flush (stderr, iostat=iostat, iomsg=iomsg) if(iostat.ne.0)then write(*,*)’ERROR:’//trim(iomsg) error stop 1 endif flush (stdout, err = 999 ) stop 999 continue stop 10 end program demo_flushFortran intrinsic descriptions (license: MIT) @urbanjost
| Nemo Release 3.1 | flush (7fortran) | August 19, 2024 |
