Text::sprintfn(3) Drop-in replacement for sprintf(), with named parameter support


This document describes version 0.07 of Text::sprintfn (from Perl distribution Text-sprintfn), released on 2015-01-03.


use Text::sprintfn; # by default exports sprintfn() and printfn()
# with no hash, behaves just like printf
printfn '<%04d>', 1, 2; # <0001>
# named parameter
printfn '<%(v1)-4d>', {v1=>-2}; # <-2 >
# mixed named and positional
printfn '<%d> <%(v1)d> <%d>', {v1=>1}, 2, 3; # <2> <1> <3>
# named width
printfn "<%(v1)(v2).1f>", {v1=>3, v2=>4}; # < 3>
# named precision
printfn "<%(v1)(v2).(v2)f>", {v1=>3, v2=>4}; # <3.0000>


This module provides sprintfn() and printfn(), which are like sprintf() and printf(), with the exception that they support named parameters from a hash.


sprintfn $fmt, \%hash, ...

If first argument after format is not a hash, sprintfn() will behave exactly like sprintf().

If hash is given, sprintfn() will look for named parameters in argument and supply the values from the hash. Named parameters are surrounded with parentheses, i.e. ``(NAME)''. They can occur in format parameter index:

 %2$d        # sprintf version, take argument at index 2
 %(two)d     # $ is optional
 %(two)$d    # same

or in width:

 %-10d       # sprintf version, use (minimum) width of 10
 %-(width)d  # like sprintf, but use width from hash key 'width'
 %(var)-(width)d  # format hash key 'var' with width from hash key 'width'

or in precision:

 %6.2f       # sprintf version, use precision of 2 decimals
 %6.(prec)f  # like sprintf, but use precision from hash key 'prec'

The existence of formats using hash keys will not affect indexes of the rest of the argument, example:

 sprintfn "<%(v1)s> <%2$d> <%d>", {v1=>10}, 0, 1, 2; # "<10> <2> <0>"

Like sprintf(), if format is unknown/erroneous, it will be printed as-is.

There is currently no way to escape ``)'' in named parameter, e.g.:

 %(var containing ))s

printfn $fmt, ...

Equivalent to: print sprintfn($fmt, ...).


There exist other CPAN modules for string formatting with named parameter support. Two of such modules are String::Formatter and Text::Sprintf::Named. This module is far simpler to use and retains all of the features of Perl's sprintf() (which we like, or perhaps hate, but nevertheless are familiar with).

String::Formatter requires you to create a new formatter function first. Text::Sprintf::Named also accordingly requires you to instantiate an object first. There is currently no way to mix named and positional parameters. And you don't get the full features of sprintf().


Text::sprintfn works by converting the format string into sprintf format, i.e. replacing the named parameters like "%(foo)s" to something like "%11$s".


Currently the main downside is speed. On my computer, sprintfn() is about two orders of magnitude slower than plain sprintf(). A simple benchmark on my PC (Core i5-2400 @ 3.1GHz):

 $ bench -MText::sprintfn -n -2 'sprintf("%s %d %d", "one", 2, 3)' 'sprintfn("%(str)s %d %d", {str=>"one"}, 2, 3)'
 Benchmarking a => sub { sprintf("%s %d %d", "one", 2, 3) }, b => sub { sprintfn("%(str)s %d %d", {str=>"one"}, 2, 3) } ...
 a: 13666654 calls (6831551/s), 2.001s (0.0001ms/call)
 b: 72461 calls (35045/s), 2.068s (0.0285ms/call)
 Fastest is a (194.9x b)


Common mistake 1



instead of


Common mistake 2 (a bit more newbish)


 sprintfn $format, %hash, ...;

instead of

 sprintfn $format, \%hash, ...;

Alternative hashes

You have several hashes (%h1, %h2, %h3) which should be consulted for values. You can either merge the hash first:

 %h = (%h1, %h2, %h3); # or use some hash merging module
 printfn $format, \%h, ...;

or create a tied hash which can consult hashes for you:

 tie %h, 'Your::Module', \%h1, \%h2, \%h3;
 printfn $format, \%h, ...;


Please visit the project's homepage at <https://metacpan.org/release/Text-sprintfn>.


Source repository is at <https://github.com/sharyanto/perl-Text-sprintfn>.


Please report any bugs or feature requests on the bugtracker website <https://rt.cpan.org/Public/Dist/Display.html?Name=Text-sprintfn>

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


perlancar <[email protected]>


This software is copyright (c) 2015 by [email protected].

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.