How do I use sprintf to zero fill to a variable length in Perl?

perl printf zerofill
Michael Shnitzer picture Michael Shnitzer · Mar 18, 2010 · Viewed 14.8k times · Source

I want to use Perl's sprintf to zerofill a variable.

sprintf("%08d", $var);

But I want to dynamically determine how many digits to zerofill.

How do I replace the "8" in sprintf("%08d", $var) with a variable called $zerofill?

Answer

brian d foy picture brian d foy · Mar 18, 2010

The first argument to sprintf is just a string:

 my $zerofill = 9;
 my $number = 1000;
 my $filled = sprintf "%0${zerofill}d", $number;

Notice the braces to set apart the variable name from the rest of the string.

We have this particular problem as a slightly clever exercise in Learning Perl to remind people that strings are just strings. :)

However, as mobrule points out in his answer, sprintf has many features to give you this sort of flexibility. The documentation for such a seemingly simple function is quite long and there are a lot of goodies in it.

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