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Re^2: Detecting last line and blank line

by haukex (Abbot)
on Nov 07, 2017 at 05:27 UTC ( #1202901=note: print w/replies, xml ) Need Help??

in reply to Re: Detecting last line and blank line
in thread Detecting last line and blank line

Anonymous Monk: eof is indeed useful, and just to add two points to what davido wrote, there are two peculiarities when it is used in while (<>) loops, including the implicit ones from the -n and -p command line switches. First, eof with and without empty parentheses is different - from its docs:

In a while (<>) loop, eof or eof(ARGV) can be used to detect the end of each file, whereas eof() will detect the end of the very last file only.

Second, davido's code example uses the line counter $., which does not get reset for each file in a while (<>) loop. To do that, you need close ARGV explicitly, that is:

while (<>) { # your code here } continue { close ARGV if eof; # Not eof()! }

This is normally done in a continue block because that way, it will still be executed even if you use next inside the loop.

As for blank lines, I like to use next unless /\S/; to skip lines that contain only whitespace. That doesn't exactly meet your "0 characters" requirement - as LanX said, use eq to compare the line to "" after chomp (or to "\n" before).

Although you don't say why you need to detect blank lines and the last line, note that setting $/=""; means files will be read in "paragraph mode", that is, records will be separated by one or more blank lines.

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