Perl Refreshments ⌘

Printing #2 - sprintf Examples

Example:

printf

As with pattern-matching and regexes, the printf function has special metacharacters to determine how to format strings. Buckle up ...

%% - a literal percent sign
%b - an unsigned integer, in binary
%B - like %b, but using uppercase "B" with the # sign
%c - a character with the given ordinal value
%d - signed integer in decimal
%e - floating-point number in scientific notation, with lowercase "e"
%E - like %e, but using uppercase "E"
%f - floating-point number in fixed decimal notation
%g - floating-point number in %e or %f notation
%G - like %g, but with uppercase "E" if applicable
%h - a C signed or unsigned short
%n - stores the number of C characters output so far into the next argument
%o - unsigned integer in octal
%p - a pointer (Perl value's address in hexadecimal)
%s - a string of unspecified width
%u - unsigned integer in decimal
%x - unsigned integer in hexadecimal using lowercase letters
%X - unsigned integer in hexadecimal using uppercase letters

Another way of looking at them ...

Integers	Floating Point	Strings
%b %B %d %h %o %p %u	%e %E %f %g %G	%c %s

There are others available for specifying numeric conversion, but we will leave that for another time (maybe).

Hold on, we're not quite done yet. Between the % sign and the formatting letter, we can also use the following attributes to control the format:

[ space ]	Prefix a positive number with a space
+	Prefix a positive number with a plus sign
-	Left-justify within the field
0	Use zeroes, not spaces, to right-justify
#	Prefix nonzero octal with "0"; nonzero hex with "0x"; nonzero binary with "0b"
*	Use value of next argument as field width
number$	Use value of "number" at position "number"
*number$	Use value of argument at position "number" as field width
number	Minimum field width (there is no maximum)
. number	Precision: digits after the "dot" for floating-point numbers, maximum length for string, minimum length for integer

OK, I'm sure we all need some examples.

Here are some formatting examples of a floating point number:

my $numb=1234.567890;
print "\n\$numb: $numb\n";
my $numbFort = sprintf "-->% d<--",$numb;
print "\n$numbFort\n"; # prefix with space
$numbFort=sprintf "-->%%$numb<--\n",$numb;
print "\n$numbFort\n"; # prefix with percent sign
$numbFort=sprintf "-->%*s<--\n",12,$numb;
print "\n$numbFort\n"; # print in # 12 char. field
$numbFort=sprintf "-->%.5d<--\n",$numb;
print "\n$numbFort\n"; # pad with 0 for 5 char. integer

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