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How do you write to the middle of a file?

by Anonymous Monk
on Jan 31, 2000 at 06:13 UTC ( #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";

[download]
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;

[download]

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