Hello to all monks.
I'm trying to do fast reading from a file. File could be arbitrarily large, so i can't read it into memory. I know the line number which i want to read (eg. just befor this line, so next readline() will get right line). My current way is this.
# Reads in
#  -filehandle: file to be moved in
#  -scalar: current line (0 is before first row)
#  -scalar: wanted line (beginning, so if read increment too)
sub Set_line (\*\$\$) {
  my $fh_r=shift @_;
  my $cur_r=shift @_;
  my $row_r=shift @_;

  if ($$cur_r>$$row_r) {
    seek ($$fh_r,0,0);
    $$cur_r=0;
  }
  while (!(($$cur_r)==$$row_r) && $_ ne "") {
    $_=readline($fh_r);
    $$cur_r++;
  }
  return;
}

[download]
Atm. i'm reading info on Tie::File (which should allow read/write, but i'm not intrested on write to that file).

In reply to Fast way to read from file by Hena

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.