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Re^3: command line perl reading from STDIN

by perlhappy (Novice)
on Jan 22, 2013 at 18:12 UTC ( #1014749=note: print w/ replies, xml ) Need Help??


in reply to Re^2: command line perl reading from STDIN
in thread command line perl reading from STDIN

Actually, I think I've just worked it out my head. Took a bit of thinking but this is what i think it is doing
first line gets sent, but because <> is unassigned (before $s), it skips; then reads the second line and assigns $s to the line and does whatever; then reads third line but because <> is unassigned, it skips; reads fourth line and the same happens; restarts with 5 line but again because <> is unassigned before the $s it skips; reads 6th line and assigns it to $s and does whatever again
this continues until end of file

If this is incorrect, let me know. Otherwise I hope this helps anyone else who might look at it. Thanks for your help choroba


Comment on Re^3: command line perl reading from STDIN
Re^4: command line perl reading from STDIN
by Anonymous Monk on Jan 23, 2013 at 23:32 UTC
     perl -ne ' $s=<>; <>; <>; do_something_with_$s'

    is equivalent to

     perl  -e ' while (<>) { $s=<>; <>; <>; do_something_with_$s} '

    so 4 lines will be read each pass, but only the second line will be used for anything

    Personally, I'd go with something like

     perl -ne 'chomp; print length($_)."\n" if (/^@/);'

    instead.

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