Hi, I have a program which modifies a file in place using a temporary file 
open(OLD, "< $old")         or die "can't open $old: $!";
open(NEW, "> $new")         or die "can't open $new: $!";
my @array = <OLD>;
my $required_element_details = shift(@array);

foreach my $remaining_details (@array) {
print NEW "$remaining_details";
}

close(OLD)   
close(NEW)                 

rename($new, $old)

[download]
Problem is this file can be accessed at the same time by the same program so the reading and writing process needs to be locked. Have tried: 
open(OLD, "< $old")         or die "can't open $old: $!";
open(NEW, "> $new")         or die "can't open $new: $!";
flock (OLD, 2);
flock (NEW, 2);

[continue as before including renaming the file before the filehandles
+ are closed]

[download]
But this doesn't work when both programs are trying at the same time, instead both programs read the same initial element (and write the same results). Any suggestions? Colin

In reply to file lock and update by CColin

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