How to delete a particular line in a text file after some operation on that text file at the same time

Question

I am perl bginner (but i guess logic is same for all programming languages like C++ and C in my case its perl).

What i want to achieve ?

I have a text file i read that file which contains different IPaddress Time in each line and when i find a particular Time then i delete that line.

What is the problem ?

The problem is when i open a file and check for time (to see that is this the particular time i am looking for to delete this line) then it need to read that file (I mean '<' operation) but when i have to delete that particular line after finding that correct time i need to do write operation (I mean this '>' operation). Now when i try to achieve this i use this code (which will surely not work as the file is opened in read mode we cannot delete (i mean write to it)):

 open my $fhi, '<', 'C:\shekhar_Axestrack_Intern\WindowCreation\ListOfIpAdress.txt', or die "Could not open file $!";
    while (my $line = <$fhi>) 
    {   
       ## Doing some operation using $fhi in read mode
        if($Time >'33')
        { 
          $fhi->autoflush; #flush the line if time is greater than 33 hours, whereas all other lines which do not folow the condition are still present in file.
        }
    }
    close $fhi;

How to delete that particular line in text file (after some manupulation of time ?)

Answer 1

You can use Tie::File:

tie @lines,'Tie::File','C:\...';
for $line (@lines){
    # Do some operation on $line
    # Test if you need to delete the line
    push @to_delete, $i++ if $need_to_delete;
}
delete @lines[@to_delete]

Note that the variable @lines becomes magical: each element of the array is a line from the file and any changes you make to that element are reflected in the file. No safety net so make a backup first!!