printf with variable display width

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

Dear Monks

I have the following print statement which looks just a little bit odd to me

$a = 10 ;
$b = 123456 ;
printf "%${a}d", $b ; # instead of printf "%10d", $b ;
[download]

Is this the correct way to use printf ?

Thanks
LuCa

Comment on printf with variable display width Download Code

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Re: printf with variable display width by QM (Parson) on Jun 14, 2006 at 16:28 UTC
That's one way to do it. I prefer the clearer method shown at sprintf: (minimum) width. The equivalent would then be: `printf "%*d", $a, $b;` [download] -QM -- Quantum Mechanics: The dreams stuff is made of	[reply] [d/l]
Re: printf with variable display width by ikegami (Patriarch) on Jun 14, 2006 at 16:43 UTC
If you're accepting `$a` from an untrusted source — aren't they all? — don't forget to validate it. Don't use `$a` and `$b` as general purpose variables. They are special and reserved for `sort` callbacks.	[reply] [d/l] [select]
Re: printf with variable display width by lukeyboy1 (Beadle) on Jun 14, 2006 at 16:24 UTC
Yes, it does work. Try this, for example: `$a = 1.2; $b = 123456 ; printf "%${a}f", $b ; # instead of printf "%1.2f", $b ;` [download] to see it use the equivalent of %1.2f (quite why you'd want this, is another matter...!). Cheers, -L-	[reply] [d/l]
Re: printf with variable display width by dsheroh (Monsignor) on Jun 14, 2006 at 16:27 UTC
It is a correct way to use it, just so long as it does what you want it to. I wouldn't say it's the correct way, as there are times when it's appropriate and times when it's overkill. TIMTOWTDI and all.	[reply]