pack/unpack left padding

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear Wise Monks,

I have fixed-width data file where numbers are padded on the left. I want to be able to use unpack to extract these number, but unpack wants the data to the right-padded. What can I do?

print '>' . unpack('A6','123   ') . "<\n";
# prints >123<
print '>' . unpack('A6','   123') . "<\n";
# prints >   123<  <---- extra leading space??
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Re: pack/unpack left padding by moritz (Cardinal) on Sep 10, 2007 at 18:52 UTC
unpack does what the documentation says it does: it extracts six characters into a string. If you want to get rid of the whitespace padding, you can just use it in numerical context: `$ perl -wle 'print ">", 0+" 123";' >123` [download] Note that a blank is nothing special to unpack. Perl 6 in German	[reply] [d/l]
Re: pack/unpack left padding by ikegami (Patriarch) on Sep 10, 2007 at 19:13 UTC
`0+$n` works great for numbers, as mentioned already. Here's a more general solution: `$n =~ s/^\s+//;` [download]	[reply] [d/l] [select]
Re: pack/unpack left padding by Skeeve (Parson) on Sep 10, 2007 at 18:52 UTC
how about `(unpack('A6',' 123')+0)` `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]