G'day...
On Wed, 2004-11-24 at 23:10, FlashMX wrote:
> To be able to do a grep on a file via a perl script do you have to read the
> whole file in before performing the search and replace? I've been hearing
> that reading the whole file in takes up
> memory and if multiple users are running the script then you better have alot
> of swap and memory.
>
> Is this correct?
Yes and No... You can read a whole file in and perform changes, and
then write out the differences to the same filename...
This may or may not take up much memory... a 23K file is only 23K after
all... it all depends on your averages...
> If this is the case how else could I do a grep to do a search and replace
> without using all the resources?
You can also read a file in a line at a time, perform the search and
replace on each line, and write the output to a new file... then at the
end replace the old file with the new one...
E.g.
open (INFILE, "< $filename");
open (OUTFILE, "> $filename.$$");
for my $line (<INFILE>) {
$line =~ s/old/new/gi;
print OUTFILE $line;
}
close(OUTFILE);
close(INFILE);
rename("$filename.$$","$filename");
Get yourself a copy of ORA's "Learning Perl" for starters...
HTH...
All the best...
-Mike
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