Cheers - L~R

Update: You don't even need to write code to read the array if you make a copy of the original file. You can just use pop and shift to create the new file. This will leave the original file empty unless you have copied it first. If you do not want to copy the file, then you will have to write your own logic.

You can't write to the beginning of a file without overwriting data that is already there. Provided the file is not to big this is the easiest (but not the only) way to do it:

my ( @data, $cnt);
while(<DATA>) {
    if ( $cnt++ % 2 ) {
        push @data, $_;
    }
    else {
        unshift @data, $_;
    }
}

# now open new file and just do (to the FILEHANDLE not STDOUT)
print STDOUT @data;

__DATA__
1
2
3
4
5
6
7
8
9
10
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This will rearrage the file to look like:

9
7
5
3
1
2
4
6
8
10
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Another option is to write one half of the data to one file and the other half (alternate lines) to another temp file. As you can see the even lines will be in the right order. The odd lines need reversing. To generate the output file use File::ReadBackwards on the odd line file to pring it out in reverse and then just print out the even lines. This is the way to do it if the file is too big to fit in an array in memory, otherwise I would not bother. You could also use Tie::File and probably a few other things as well.

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

I notice you call your output file '-randomize' which it is most certainly not. If you want to make a random arrangement of lines then do a Fisher-Yates Shuffle

open FILE, $file or die $!;
my @array = <FILE>;
close FILE;
my $i = @array; 
while( $i-- ){
    my $j=int rand(1+$i);
    next if $i == $j;
    @array[$i, $j]=@array[$j, $i]
}

open OUT, ">$out" or die $!;
print OUT @array;
close OUT:
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Use Tie::File if you can't fit the entire file in an array in memory but don't expect if to finish in a hurry.

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

Just sticking text in at the beginning of the file will not make the rest of the file move out of the way, your code will need to do the work of moving the other data to make room for the new line. If the file is small enough to hold in memory, this may be an easier randomizing technique:

open(FIN,"<$ARGV[0]") or die "Input file: $!";
chomp(@data = <FIN>);
close(FIN);

open(FOUT,">$ARGV[0]-randomized") or die "Output file: $!";
while(@data) {
    print FOUT splice(@data,rand(@data),1)."\n";
}
close(FOUT);
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my @index;
do {push @index, tell FIN} while <FIN>;
pop @index;
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Then you can read lines from the file in any order you want, using seek with elements of @index, and print them to the output file in sequence. For example, to read and print the 5th line from the input file:

seek FIN, $index[4], 0;
print FOUT scalar <FIN>;
[download]