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

There are three commonly proposed methods to do this:

Read the entire file

@array = <FILE>;
$last_line = $array[$#array];
[download]

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
[download]

Use File::ReadBackwards

tie *FILE, File::ReadBackwards 'input_file';
while (<FILE>) {
   # line-by-line starting from the end
}
[download]

This latter method is supposed to be efficient and fast, so I imagine it uses some variation of the seek() method above.

Comment on Re: How do I copy out the last line written in a file? Select or Download Code

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Re: Answer: How do I copy out the last line written in a file? by Anonymous Monk on May 03, 2007 at 01:56 UTC
When a file is read into an array the last element in the array array-1 would give you what you are looking for. Shashidhar Iddamsetty	[reply]
Re^2: Answer: How do I copy out the last line written in a file? by blazar (Canon) on May 03, 2007 at 10:18 UTC
When a file is read into an array the last element in the array array-1 would give you what you are looking for. To put it more clearly, and in actual Perl rather than some pseudo-language, the first example above, i.e. `@array = <FILE>; $last_line = $array[$#array];` [download] could be rewritten like `@array = <FILE>; $last_line = $array[-1];` [download] or even without creating an intermediate `@array`: `my $last_line = (<FILE>)[-1];` [download] Incidentally, I put a my in front of that as a reminder of the good rule of always staying strict.	[reply] [d/l] [select]