Linux / Unix : how to see the hidden files?

When working in the linux / unix, need to list out the hidden files or directories. For example your home directory have hidden files like .profile.

To display hidden files, the ls command have option.

Linux / Unix : who is currently in the system? What they are doing?

To get the list of users currently loggged in the system, we can use who, users and w commands.

Perl Hash and Array numerical and alphabetical Sorting

Sorting Array in numerical Order

my @numbers = (1,2,10,11,100,22,20);

#sorting array in numerical order
print "\n\n Sorting Array in Numberical Order\n\n";
foreach my $num ( sort {$a <=> $b} @numbers) {

print $num."\n\n";
}

IMS - DB Components

IMS(Information Management System) is IBM's hierarchical database product. For many years, IMS was the most popular database for IBM mainframes. IMS consists of two components:

  1. DB, or Database and
  2. DC, or Data Communications.

Perl hash and hash reference examples

Hash is data structure like array whereas array have indices , hash has unique key strings. In hash each keys associated with values. In Perl % used to define the hash variable.

For example:

my %fruitsColor= ('Watermelon'=>'Green' ,'Apple'=>'Red','Orange'=>'Orange');

 

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