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How do I copy out the last line written in a file?

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Contributed by Anonymous Monk on Sep 19, 2000 at 01:41 UTC
Q&A  > files

Answer: How do I copy out the last line written in a file?
contributed by Fastolfe

There are three commonly proposed methods to do this:

Read the entire file

@array = <FILE>; $last_line = $array[$#array];
This involves reading the entire file before examining the last line, which can be costly in memory and performance for large files.

Seek to the end and backtrack

seek(FILE, -81, 2); # 81 bytes from the end, which should +be enough @lines = <FILE>; $last_line = $lines[$#lines]; # similar to above, but we don't read +much
Use File::ReadBackwards
tie *FILE, File::ReadBackwards 'input_file'; while (<FILE>) { # line-by-line starting from the end }
This latter method is supposed to be efficient and fast, so I imagine it uses some variation of the seek() method above.
Answer: How do I copy out the last line written in a file?
contributed by merlyn

And don't forget File::Tail, which can keep up with the file as it grows (of which this request is often a part).

Answer: How do I copy out the last line written in a file?
contributed by I0

use Tie::File:

use Tie::File; sub last_line_of_file { my $file = shift; tie my @array, 'Tie::File', $file or die "read $file - $!"; $array[-1] }

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