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7.12. Storing a File Inside Your Program Text

7.12.1. Problem

You have data that you want to bundle
with your program and treat as though it were in a file, but you
don''t want it to be in a different file.

7.12.2. Solution

Use the _ _DATA_
_ or _ _END_ _ tokens after your program
code to mark the start of a data block, which can be read inside your
program or module from the DATA filehandle.

Use _ _DATA_ _ within a module:

while ( <DATA>) {
# process the line
}
_ _DATA_ _
# your data goes here

Similarly, use _ _END_ _ within the main program
file:

while (<main::DATA>) {
# process the line
}
_ _END_ _
# your data goes here

7.12.3. Discussion

The _ _DATA_ _ and _ _END_ _
symbols tell the Perl compiler there''s nothing more for it to do in
the current file. They represent the logical end for code in a module
or a program before the physical end-of-file.

Text after _ _DATA_ _ or _ _END_
_ can be read through the per-package
DATA filehandle. For example, take the
hypothetical module Primes. Text after _ _DATA_ _
in Primes.pm can be read from the
Primes::DATA filehandle.

_ _END_ _ behaves as a synonym for _
_DATA_ _ in the main package. Any text occurring after an
_ _END_ _ token in a module is completely
inaccessible.

This lets you write self-contained programs instead of keeping data
in separate files. Often this is used for documentation. Sometimes
it''s configuration data or old test data that the program was
originally developed with, left lying about should it ever be needed
again.

Another trick is to use
DATA to find out the current program''s or module''s
size or last modification date. On most systems, the
$0 variable will contain the full pathname to your
running script. On systems where $0 is not
correct, you could try the DATA filehandle
instead. This can be used to pull in the size, modification date,
etc. Put a special token _ _DATA_ _ at the end of
the file (and maybe a warning not to delete it), and the
DATA filehandle is available to the script itself.

use POSIX qw(strftime);
$raw_time = (stat(DATA))[9];
$size     = -s DATA;
$kilosize = int($size / 1024) . "k";
print "<P>Script size is $kilosize\n";
print strftime("<P>Last script update: %c (%Z)\n", localtime($raw_time));
_ _DATA_ _
DO NOT REMOVE THE PRECEDING LINE.
Everything else in this file will be ignored.

If you want to store more than one file in your program, see Recipe 7.13.

7.12.4. See Also

The "Scalar Value Constructors" section of
perldata(1), and the "Other Literal Tokens"
section of Chapter 2 of Programming Perl;
Recipe 7.13