Monitor on file

Shell Programming and Scripting
1

Hi friends
I need to monitor a file which is modified or not. if modified i need to get a mail mail or error message.

Eg: monitor.cfg file

2

you can use tools like md5sum, cksum, sha1 etc to monitor your file. an alternative in Perl

#!/usr/bin/perl
use Digest::MD5 ;
my $file2monitor = "file";
sub getmd5 {
    my $file = $_[0];    
    open(FH,"<",$file) or die "Cannot open file: $!\n";    
    binmode(FH);
    my $md5 = Digest::MD5->new;
    return $md5->addfile(*FH)->hexdigest;    
    close(FH);
}
my $original_sum = getmd5 $file2monitor;
while (1){
    my $getcksum = getmd5 $file2monitor;
    if ( $getcksum ne $original_sum ){
       print "File $file2monitor changed:\n";
    }
    sleep 3;
}