I want to read in thousands of records into an array and then process them. I'm not particularly interested in that processing of the array, but instead I'm interesting in optimising the reading of the "\n" seperated data into an array (via sysread), and then the writing of it all out again.

As the data could be a couple of meg big I want as few occurences of the data being process/used as possible...

I have to have it in an array, and I have to using sysread and syswrite to read/write the record in one go cos my ISP counts IO processes...

Thanks in advance for any help...

    my $rec;
    sysopen(DF,"test.txt", O_RDONLY | O_CREAT);
    sysread(DF, $rec, -s DF);
    close DF;

    # Split up records into array.
    # Will lose \n on recs - add later.
    @test=split("\n",$rec);

    # Do some work on @test
     Work... Work... Work...

    # Build up into a single record, putting \n back in
    my $rec;foreach(@test){$rec.=$_."\n";}

    sysopen(DF,"test.txt", O_WRONLY | O_CREAT);
    syswrite DF,$rec;
    close DF;

[download]

note: This has been a little bit covered in a previous thread but someone suggested starting a new thread just for this optimisation... So here it is :)

In reply to Suggestions for optimizing this code... by NeilF

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.