Beefy Boxes and Bandwidth Generously Provided by pair Networks
Just another Perl shrine
 
PerlMonks  

How do you write to the middle of a file?

( #2608=categorized question: print w/ replies, xml ) Need Help??
Contributed by Anonymous Monk on Jan 31, 2000 at 06:13 UTC
Q&A  > files


Description:

I have a file I am using on my website, and I want to go in, at a specified spot, and change|add info to that spot. Is there an easier way besides writing to a temp file, then renaming the temp file over the old file? Thanks

Answer: How do you write to the middle of a file?
contributed by devslashneil

#!/usr/bin/perl use Tie::File; my $filename = 'foo.dat'; tie @array, 'Tie::File', $filename or die "Cannot open $filename\n"; @array[5] = "Hello, World!\n";
Answer: How do you write to the middle of a file?
contributed by Anonymous Monk

Such is the evil of the standard (read UNIX) file model. One solution is as follows:

$flen = -s $file; # file length in bytes $from = 42; # insertion point open FILE, '+<the/file.ext' or die "Couldn't open file: $!"; read FILE, $buf, ($flen - $from), $from; seek FILE, $from, 0; print FILE 'blahblahblah', $buf;

Please (register and) log in if you wish to add an answer



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • 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, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            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.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others contemplating the Monastery: (22)
    As of 2014-10-30 15:10 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      For retirement, I am banking on:










      Results (208 votes), past polls