On May 9, 1:29 pm, demianricca...@gmail.com (D) wrote:
> Hello everyone,
>
> I would like to learn an efficient way to change a single column in a
> file that is accessed by an external program after the column is
> changed each time. open write close is what I have been using. I
> thought that tieing could help speed it up. While I didn't dig in too
> deeply, my split entry, change value and rejoin didn't seem to gain me
> much speed. The test file and script are pasted below. In practice
> the file will be about 100 lines long and the 3rd column will be
> rewritten thousands of times. Is there a more efficient approach?
>
> example file:
>
> 'test'
> -------------
> foo ab 0
> fooa b 0
> foob cd 0
> foo e 0
> fooc f 0
> foo ab 0
> fooa b 0
> foob cd 0
> foo e 0
> fooc f 0
> -------------------------
>
> script:
> -------------------------------
> use IO::All;
> use warnings;
> use strict;
>
> my $lines = io('test')->new;
>
> print "$_ \n" foreach @$lines;
> print "\n\n\n\n\n";
>
> my @tmp;
> foreach (0 .. $#{$lines}){
> $tmp[$_] = $_;
>
> }
>
> @$lines = map {
> my @sh = split /\s+/, $lines->[$_];
> join(" ",$sh[0],$sh[1],$tmp[$_]);
> } 0 .. $#{$lines};
>
> --------------------------
>
> cat test:
>
> foo ab 0
> fooa b 1
> foob cd 2
> foo e 3
> fooc f 4
> foo ab 5
> fooa b 6
> foob cd 7
> foo e 8
> fooc f 9
> foo ab 10
the tie that you mentioned is actually a decent
alternative if speed's not an overriding issue.
For example:
use DB_File;;
tie my %HASH, "DB_File", $file,
O_CREAT|O_RDWR, 0666, $DB_HASH
or die "error opening $file: $! ";
my @valid_keys = ('foo ab', 'fooa b', ... ); # valid keys
foreach my $key (@some_keys) {
$HASH{ $key } = 'new value'
if grep( $key eq $_, @valid_keys );
}
--
Charles DeRykus
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