open()

[Fairlight]

On Thu, Mar 06, 2014 at 10:28:52AM +1000, Scott thus spoke:
> Hi all 
> 
> Can anyone please explain the use of open () or create() with the
> 
> LF = open ("path/filename", "rwct")
> 
> "filename" is the name of the file to be opened.
> "mode" is the access mode to use (see below).
> "aa" is the file handle.
> 
> Parameters
> 
> mode  r - read access
>       w - write access
>       c - create if doesn't exist
>       0 - truncate if already exists
>       b - binary mode
>       t - text mode
> 
> & er = writeline(lf,sq)
> 
> sq being the sql statement
> 
>      Then: bytes = WRITELINE(handle,source,length)
>        Then: bytes = WRITELINE(handle,source)
> 
> "handle" is the file handle returned by OPEN() or CREATE().
> "source" is the data to write.
> "length" is the number of bytes to write.
> 
> "bytes" is the number of bytes written, including newline
> 
> If length is not specified, the length of the source field is used.
> 
> A newline character is appended to the information written.
> 
> Return value
> 
> The number of bytes written, including the newline.
> 
> Note: The file must be opened in text mode. A newline character is appended
> to the information written.
> 
> Yet each time a new record is done in the rreport it dumps over previous
> lines/file.
> 
> FP Ver 4.8.13 Windows

Your problem is that open() in filePro has many flags, including 't' for
truncate (equivalent to O_TRUNC in the underlying C function open(2)), but
it has no analog for O_APPEND, and O_APPEND is not logically ORed to the
rest of the flags as the default behaviour.

What you really want to do is focus on this:

4.5  SEEK               Set the current location within an opened file.

      Syntax:

           aa = SEEK(handle,offset,whence)
           aa = SEEK(handle,offset)

        Where handle is the file handle returned by OPEN() or
        CREATE(), offset is the position within the file, and
        whence flags how to interpret the offset.

      Parameters
          whence    0 - absolute position in the file
                    1 - position relative to the current position
                    2 - position relative to end-of-file

      Return value: The resulting absolute position in the file.

      Notes: Offset can be negative when using relative positioning.

Right after your open(), do this:

aa=seek(lf,"0","2")

That will set you up to append to the end of the file.

mark->
-- 
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