Using the printf and sprintf functions
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The Perl printf is much like the
printf function in C and awk in that it takes a string to be formatted
and a list of format arguments, applies the formatting to the string, and
then typically prints the formatted string to standard output, which in
our case, is the Web browser.
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The printf syntax uses a double quoted string which includes special format
markers followed by a comma-delimited list of arguments to be applied to
those markers. The format markers are typically in the form of a percent
sign followed by a control character.
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For example, the generic format of printf might look like the following
code:
printf ("[some text] %[format] [other text]",
[argument to be formatted]);
In usage, we might use the %s formatting argument specifying a string and
the %d formatting argument specifying a digit using the following syntax:
#!/usr/local/bin/perl
print "Content-type: text/html\n\n";
$name = "Selena Sol";
$age = 28;
printf ("My name is %s and my age is %d.\n",
$name, $age);
The code above would produce the following output in the Web browser window:
My name is Selena Sol and my age is 28.
In reality, the printf function is rarely used in Perl
CGI since, unlike C which almost demands the use of printf, Perl has much
easier ways of printing. However, the printf routines are essential for
another, more useful (to CGI developers) function, sprintf.
Unlike printf, sprintf takes the formatted output and assigns it to a variable
rather than outputting it to standard output (<STDOUT>), using the following
generic syntax:
$variable_name = sprintf ("[some text]
%[format] [other text]", [string to be
formatted]);
A good example of using sprintf might come from a shopping cart script.
In this script, we need to format subtotals and grand totals to two decimal
places so that prices come out to numbers like "$99.00" or "$98.99" rather
than "99" or "98.99876453782". Below is a snippet of code which uses sprintf
to format a price string to two decimal places.
$option_grand_total = sprintf ("%.2f\n",
$unformatted_option_grand_total);
In this example, the variable, $unformatted_option_grand_total is formatted
using the "%.2f" argument which formats (%) the string to two decimal places
(.2f).
There are a multitude of formatting arguments besides "%s", "%d" and "%f",
however. The following Table lists several useful ones.
| Format character |
Description |
| c |
Character |
| s |
String |
| d |
Decimal Number |
| x |
Hexadecimal Number |
| o |
Octal Number |
| f |
Floating Point Number |
 Using
qq
Table of Contents
Formatting
the Output
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