Sequentially re-reading a file

[Mike Trader]

If I open a file for sequential reading of lines with:
OPEN MyFile.txt FOR INPUT AS #1

and read 2/3 of the contents, how do I start back at the top again?
Do I have to close the file and re-Open it? IS that the only way or is there some little GoToTop command i am missing?




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Kind Regards
Mike

[Ian Cairns]

From the help file:

SEEK [#] filenum, position

Works for sequential access (0 = top of file). It worked fine for me in DOS.

regards,

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[email protected]

[Lance Edmonds]

On a side note, to speed up reading a sequential file, add a LEN=8192 clause to the OPEN statement. For a sequential file, this tells PowerBASIC to use an internal buffer when getting data from the file, usually increasing read speed quite dramatically.

You can specify a much larger value which will improve things even more, however, when reading across a network, 8192 is about the ("rule of thumb") optimal buffer size to avoid network saturation.

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Mike Trader]

thx Ian I will try that,

Cool Lance, I wrote it like this:
OPEN SourceFile FOR INPUT AS 100 LEN = 8192

I am compiling a huge file from many smaller ones. Each "small one is 22k lines. I have about 10 of them to compile (is there a limit to the size of a .txt file?)

I assume the 8192 is the number of bytes?

Im not on a network so can I allocate a much bigger chunk of memory like say 500k or even 1MB?

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Kind Regards
Mike

[Lance Edmonds]

Correct on all counts.

The file size is a limit of the O/S, so for WIn95a it is around 2Gb, larger for latter versions of Windows (using Fat32, NTFS, etc).

PowerBASIC itself uses the QUAD integer range for byte/record access to files. Thats a lot of bytes and records!


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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>