How do I use sprintf to zero fill to a variable length in Perl?
I want to use Perl's sprintf to zerofill a variable.
sprintf("%08d", $var);
But I want to dynamically determine how many digits开发者_如何转开发 to zerofill.
How do I replace the "8" in sprintf("%08d", $var)
with a variable called $zerofill
?
The first argument to sprintf is just a string:
my $zerofill = 9;
my $number = 1000;
my $filled = sprintf "%0${zerofill}d", $number;
Notice the braces to set apart the variable name from the rest of the string.
We have this particular problem as a slightly clever exercise in Learning Perl to remind people that strings are just strings. :)
However, as mobrule points out in his answer, sprintf has many features to give you this sort of flexibility. The documentation for such a seemingly simple function is quite long and there are a lot of goodies in it.
sprintf
and printf
support the *
notation (this has worked since at least 5.8):
printf "%0*d", 9, 12345;
000012345
printf '$%*.*f', 8, 2, 456.78;
$ 456.78
I needed to do something slightly different: zero pad a floating point value and get an exact length.
In my case I need exactly 12 bytes including the decimal point. It is slightly trickier than what you have above. Here it is in case anyone needs this:
Say $inputVal is a string passed in from somewhere with a value like 1001.1. Note that it should be less than 12 characters for this to work reliably
# This will give us extra zeros, but the string may be too long
my $floatVal = sprintf('%*.*f', 12, 12, $inputValue);
# This will remove any extra zeros
$result = substr($floatVal, 0, 12);
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