in reply to Re^2: How to use sprintf %n formatting pattern
in thread How to use sprintf %n formatting pattern

Consider:

my $str = '1234567890' x 6;
my $prefixLen;

printf "Prefix stuff %n%s\n", $prefixLen, substr $str, 0, 35 - $prefix
+Len;

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What value does substr see for $prefixLen? How can printf get the substr generated parameter generated after printf has set about generating the output?

Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond

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Re^4: How to use sprintf %n formatting pattern
by hv (Prior) on Jun 09, 2022 at 11:54 UTC

    By using a sprintf parameter to determine the width:

    my $str = '1234567890' x 6;
my $prefixLen;
my $magicLimit = tie_me_a_scalar(sub { $max_width - $prefixLen });

printf "Prefix stuff %n%.*s", $prefixLen, $magicLimit, $str;

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    Update: corrected %*s to %.*s

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      It's not clear to me how a tied scalar gets around the evaluation order issue with printf's arguments. Maybe you could provide a fully worked example?

      Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond
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