#!/usr/bin/perl -w
                                                                                
# Strict
use strict;
use warnings;
                                                                                
# Main program
print "Check file before unlink\n"; sleep 1;   system("ls $0");
print "Unlinking the file $0\n";    sleep 1;   unlink $0;
print "Check file after unlink\n";  sleep 1;   system("ls $0");
                                                                                
print "File should be now be gone from disk (but still in memory)\n";
print "Try ^Z and check it with 'ls $0' ... (come back with 'fg')\n";
sleep 10;

print while <DATA>;

print "I'm still here, but the original file is long gone.\n";

__END__
foo

##</code><code>##

#!/usr/bin/perl -w
                                                                                
# Strict
use strict;
use warnings;
use File::Basename;
                                                                                
# Main program
print "Check file before unlink\n"; sleep 1;   system("ls $0; df -k $0");
print "Unlinking the file $0\n";    sleep 1;   unlink $0;
print "Check file after unlink\n";  sleep 1;   system("ls $0; df -k " . dirname($0));
                                                                                
print "File should be now be gone from disk (but still in memory)\n";
print "Try ^Z and check it with 'ls $0' ... (come back with 'fg')\n";
sleep 10;

1 while <DATA>; # ensure we use the *DATA filehandle in case perl optimises it away

print "I'm still here, but the original file is long gone.\n";

__END__
foo

##</code><code>##

$ cp z.pl /ram; perl /ram/z.pl
Check file before unlink
/ram/z.pl
Filesystem           1K-blocks      Used Available Use% Mounted on
none                       100         4        96   4% /ram
Unlinking the file /ram/z.pl
Check file after unlink
ls: /ram/z.pl: No such file or directory
Filesystem           1K-blocks      Used Available Use% Mounted on
none                       100         4        96   4% /ram
File should be now be gone from disk (but still in memory)
Try ^Z and check it with 'ls /ram/z.pl' ... (come back with 'fg')
I'm still here, but the original file is long gone.
$ df -k /ram
Filesystem           1K-blocks      Used Available Use% Mounted on
none                       100         0       100   0% /ram