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

Hi, I want to format a printf statement using a variable, i.e. if I had
printf "%-2s", $var1
how could I set the value for the format (the 2 in this case) using a variable, or is it not possible???

Thanks for any assistance

Replies are listed 'Best First'.
Re: Formating a printf statement using a variable
by mr.nick (Chaplain) on Jun 15, 2001 at 19:25 UTC
    Yes, it's quite possible: 
    $a="%-2s";
printf $a,$b;
$c="2s";
printf "%-$c",$b;

    [download]

    mr.nick ...

[reply]
[d/l]
Re: Formating a printf statement using a variable
by lemming (Priest) on Jun 15, 2001 at 19:26 UTC
    Try it out and see! 
    use strict;
use warnings;

my $fmt = "%2.2f %02d %s\n"

printf $fmt, 4.4, 3, "ta da!";

    [download]
[reply]
[d/l]
      Thanks to you all for the quick response, it now is working
[reply]
Re: Formating a printf statement using a variable
by tadman (Prior) on Jun 15, 2001 at 20:31 UTC
    The "old fashioned" way of doing this, without string interpolation, is like so:      printf ("%-*s", 2, $var1); Where the asterisk indicates that the width of the field is supplied as an argument, which in this case is 2 but could easily be a variable or result of a calculation.

    Update: Albannach was kind enough to point out that this feature of the Perl printf was added in version 5.004. Historically, C compilers have supported this method since the beginning of time, since there is no built in "string interpolation" method.
[reply]
[d/l]
Re: Formating a printf statement using a variable
by Marza (Vicar) on Jan 10, 2003 at 02:37 UTC

    I just love this place. I had a simliar issue and bam here is the answer on the search.

    A differnt version of the question involved displaying columnized data.

    If a word was larger then a certain size then I needed differnt columns and a print size. Using the offered method:

    use strict;
use warnings;

my $fmt = "%-$print_size" . "s";
printf("$fmt","$_");

    [download]

    Thanks again and though it is late ++all

[reply]
[d/l]
      Why not simply so? printf "%-${print_size}s", $_;

      Also note the lack of quotes around $_ - if you just refer to a variable by itself, don't interpolate it. There are cases where you need to do that, but you'll know them when you come across them. Most of the time it's just a wasted node in the optree and can even break code that would work fine without the quotes.

      HTH

      Makeshifts last the longest.

[reply]
[d/l]

        Even better! Thank you! One less line and variable! I didn't know you could do that! ;-)

[reply]

Back to Seekers of Perl Wisdom