The cal command is a utility in Linux that is used to display a calendar on the command line. It provides a simple and convenient way to view the calendar for a specific month or year. The cal command is part of the util-linux package, which is a collection of essential utilities for Linux.

The cal command is primarily used for quickly checking dates, planning events, and scheduling tasks. It is especially useful for system administrators, developers, and users who work extensively on the command line and need a quick way to view the calendar without opening a separate application.

Official page of cal (View a command-line calendar): https://man7.org/linux/man-pages/man1/cal.1.html

The cal command is written in C programming language.

Installation on Supported Operating Systems

The cal command is included by default in most Linux distributions. To check if it is installed on your system, open a terminal and type:

cal

If the cal command is not found, you can install it using the package manager specific to your Linux distribution:

Ubuntu/Debian:

sudo apt-get install util-linux

Red Hat/Fedora:

sudo dnf install util-linux

CentOS:

sudo yum install util-linux

Examples of cal (View a command-line calendar) commands

Display the calendar for the current month:

cal

This command will display the calendar for the current month, with the current day highlighted.

Display the calendar for a specific month:

cal 10 2022

This command will display the calendar for October 2022.

Display the calendar for a specific year:

cal -y 2022

This command will display the calendar for the year 2022.

Display the calendar for a specific month and year:

cal 10 2022

This command will display the calendar for October 2022.

Similar commands and benefits

There are several other commands and utilities available in Linux that provide similar functionality to the cal command:

• date: The date command is used to display the current date and time. It can also be used to format and manipulate dates.
• ncal: The ncal command is an alternative to the cal command that provides additional features, such as displaying the calendar in a different format and highlighting the current date.
• gcal: The gcal command is a more advanced calendar utility that provides features like displaying holidays, customizing the output format, and supporting different calendar systems.

The cal command is lightweight and simple, making it ideal for quick calendar checks and basic scheduling tasks. It is widely used by system administrators, developers, and users who work extensively on the command line.

Scripts using cal (View a command-line calendar)

Script 1: Display the calendar for the current month

#!/bin/bash
cal

This script will display the calendar for the current month when executed.

Script 2: Display the calendar for a specific month and year

#!/bin/bash
read -p "Enter the month (1-12): " month
read -p "Enter the year: " year
cal $month $year

This script prompts the user to enter a month and year, and then displays the calendar for that month and year.

Script 3: Display the calendar for the current month and highlight weekends

#!/bin/bash
cal -h

This script will display the calendar for the current month and highlight weekends (Saturday and Sunday) when executed.

List of cal (View a command-line calendar) functions and constants

Function/Constant	Description
cal	Displays the calendar for a specific month or year.
ncal	An alternative to the cal command with additional features.
gcal	A more advanced calendar utility with additional features.
date	Displays the current date and time.

Conclusion

The cal command is a simple and convenient utility in Linux that allows users to view a calendar on the command line. It is widely used by system administrators, developers, and users who work extensively on the command line. The cal command provides a quick way to check dates, plan events, and schedule tasks without the need for a separate calendar application. It is lightweight, easy to use, and comes pre-installed in most Linux distributions. The cal command is written in C programming language and is part of the util-linux package.

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