如何在Windows上使用裸露的Perl读取文件的最后一行？

Question

I need to read only the last line of a file, without using File:ReadBackwards module as it is not installed on my remote server(windows) where I need to execute the script. Kindly suggest the most efficient way to read only the last line.

Answer 1

This answer does not work on Windows.

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If this is a one-off thing, simply do a system call and use tail .

my $last_line = `tail -n 1 $filename`;

If you need to do this a lot, think about installing into a local-lib on the remote machine, or fatpacking File::ReadBackwards into your script before you deploy it.

Answer 2

You are in windows. I don't know what are the inbuild command for windows but you try something like as follows

Iterate the file handler with while loop and store the output in variable then print it

open my $fh ,"<","file.txt";
my $last_line;
$last_line = $_,while (<$fh>);
print $last_line;

or else try the follow but these are consume more memory.

open my $fh ,"<","file.txt" or die "error opening $!";
my @ar = <$fh>;
print $ar[-1];

Or else

open my $fh ,"<","file.txt" or die "error opening $!";
my @ar = <$fh>;
print pop @ar;

Answer 3

If you know something about the files (if the lines are relatively equal lengths, or if each line is at most X bytes, or whatever) you might be able to do something with seek. For example, if the last line is at most 40 bytes or so, you can do the below. If you know the file is 100 MB (using File::stat, which is core) you could average the first 10 lines and see how many bytes they are, and maybe multiply that by 5 just in case and seek back that far and then do the loop. You might have to read 15 or 20 lines, but that's not bad.

open(my $input,"input2.txt")||die "can't open the file";

my $last_line;
seek ($input, -50, 2);
while(<$input>)
{
    $last_line = $_;
}

print "$last_line\n";

Answer 4

I found the following here .

Try this on for size:

system tail => -1 => $file;