Insight: Level Up Your Pi—Combining cal with Other Terminal Tricks!

Insight: Level Up Your Pi—Combining cal with Other Terminal Tricks!

Welcome, fellow Raspberry Pi explorers! You've got your Pi up and running, maybe you've tinkered with some Python, and you're starting to feel comfortable with the command line. That's awesome! Today, we're going to take a seemingly simple command – cal, which shows you a calendar right in your terminal – and see how we can combine it with other basic Linux tools to do even cooler things.

Think of the Linux command line as a set of building blocks. Each command does one thing well, but when you put them together, you can create some surprisingly useful workflows. Let's see how we can make cal play nicely with others on your Raspberry Pi!

We're assuming you have cal installed. If not, open your terminal and run the following install command:

Bash

sudo apt update && sudo apt install ncal   

Piping cal to grep: Finding Specific Dates

Imagine you want to quickly see if a specific day of the week falls on a certain date in the current month. We can use the cal command and "pipe" its output to another command called grep. grep is like a search tool for the terminal – it looks for specific patterns in text.

Let's say you want to see if any Tuesdays fall on the 15th of the current month. First, run cal:

Bash

cal   

Now, let's pipe that output to grep and search for "Tu" and "15":

Bash

cal | grep "Tu.*15"   

• The | (pipe) symbol takes the output of the cal command and sends it as input to the grep command.
• The command grep "Tu.*15" tells grep to look for lines that contain "Tu", followed by any number of characters (.*), and then "15".

If a Tuesday falls on the 15th of the current month, that line will be highlighted in the output!

You can adapt this to search for any day of the week and any date. For example, to find all Saturdays:

Bash

cal | grep "Sa"   

Using cal with date: Getting Context

Sometimes, you might want to see the calendar for a specific date you're working with. You can use the date command to get a specific date and then use a little trick to feed that into cal.

Let's say you want to see the calendar for the same month as a specific date, like March 10th, 2024. First, you can get the month and year using date with some formatting options:

Bash

date -d "March 10, 2024" "+%m %Y"   

This will output something like 03 2024. Now, we can use command substitution (using backticks `` or $()) to use this output with cal:

Bash

cal `date -d "March 10, 2024" "+%m %Y"`   

This will display the calendar for March 2024. While this example is a bit more involved, it shows how you can dynamically generate input for cal using other commands.

Displaying a Specific Date's Calendar Context

Let's combine date and cal in another way. What if you want to see the calendar for the month of a specific date, and also know what day of the week that date was?

Here's what we're going to create - a nice calendar display for May 2025 that highlights information about May 20th:

Bash

     May 2025
Su Mo Tu We Th Fr Sa
               1  2  3
 4  5  6  7  8  9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

Tuesday, May 20, 2025 is a Tuesday.

Here's the command that creates our calendar display:

Bash

cal 05 2025 && date -d "2025-05-20" "+%A, %B %e, %Y is a %A." 

Let's break down what each part does:

• cal 05 2025: Displays the calendar for May 2025.
• &&: Connects the two commands, ensuring the second runs only if the first succeeds.
• date -d "2025-05-20" "+%A, %B %e, %Y was a %A.": Displays formatted date information for May 20, 2025.

The Power of Combining Commands

These are just a few simple examples to get you thinking about how you can combine cal with other command-line tools on your Raspberry Pi. As you become more familiar with different commands, you'll discover even more creative ways to chain them together to accomplish tasks efficiently.

The beauty of the Linux command line lies in this composability. Each tool is a building block, and your imagination is the limit when it comes to constructing powerful and useful commands. So, keep exploring, keep experimenting, and have fun with your Raspberry Pi!

Need Raspberry Pi Expertise?

We'd love to help you with your Raspberry Pi projects.  Feel free to reach out to us at info@pacificw.com.

Written by Aaron Rose, software engineer and technology writer at Tech-Reader.blog.