All:
How can I read a file until I come across a piece of information, , go backwards to the start of record, and then process record from start to finish.

In the past, this is how I have accomplished it:

  • 1. Read file ignoring lines until I see start of record
  • 2. Store all lines I read in until I encounter information
  • 3. If information not a match, throw out stored information and go back to first item
  • 4. If information is a match, continue reading/storing until end of record

    The problem is that this is slow and memory intensive depending on how large the record is and how far down is the information I am searching for. I would like to use seek or something to read ignoring everything until I encounter match, read backwards to start of record, and then process the whole record.

    Here is an example of what a file would look like: 

    blank line
START OF RECORD
  LINE 1
  INFORMATION I AM LOOKING FOR  
  LINE 3
  LINE 4
  LINE 5
  LINE 6
END OF RECORD
blank line
START OF RECORD
  LINE 1
  LINE 2
  LINE 3
  LINE 4
  INFORMATION I AM LOOKING FOR  
  LINE 6
END OF RECORD

    Any ideas?

    L~R

    In reply to Read forward and backward - need help by Limbic~Region

    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.