Grok all the things

grok (v): to understand (something) intuitively.


๐Ÿ‘ถ ย Children (ELI5)

Greetings, young explorers! Today, we're diving into the incredible world of AWK, a powerful text processing tool that can transform words, numbers, and data into fantastic new forms. Think of AWK as a friendly wizard that can work magic on your computer files. Are you ready to discover its secrets? Let's go!

Once Upon a Time... ๐Ÿ“œ

In a faraway land known as Bell Laboratories, back in the ancient days (the 1970s), three wise wizards โ€“ Alfred Aho, Peter Weinberger, and Brian Kernighan โ€“ conjured up a magical tool named AWK. They combined the first letters of their last names to form the name AWK. Clever, right?

AWK was designed to help people easily search for, modify, and perform actions on text files. It became especially popular among Unix users, and AWK is still going strong today!

What's the Magic Behind AWK? ๐Ÿง™โ€โ™‚๏ธ๐Ÿ”ฎ

AWK is a text processing wizard that understands patterns and actions. When we ask AWK to cast its spell on a file, we provide it with patterns to look for and actions to perform when it finds these patterns.

Imagine you have a chest full of magical gems โ€“ like in a video game! โ€“ with each gem representing a line of text from your file. AWK will sift through the chest, examining each gem carefully. When it finds one that matches the pattern you've given it, it'll perform the action associated with that pattern.

To talk to our wizard AWK, we use spells written in its own special language. But don't worry! We'll learn how to write these spells together.

Our First Spell: AWK's Basic Structure ๐Ÿงช

Let's practice our first AWK incantation! To cast a basic AWK spell, we need to follow this simple structure:

awk 'pattern { action }' file

Here, pattern tells AWK what to look for, action tells it what to do when it finds something, and file is the name of the file where AWK will work its magic.

Psst! Fun fact: If we don't provide a pattern, AWK will perform the action on every line of the file.

Conjuring Magical Patterns ๐Ÿ”

The magical patterns we can give AWK are like secret decoder rings! Let's see some examples of these powerful symbols :

  • /apple/: This pattern will match any line containing the word "apple" . Delicious!
  • $1 > 10: This mysterious incantation matches lines where the first field has a value greater than 10. We'll learn more about fields soon!

Remember, if we don't provide a pattern, AWK will apply the action to every line in the file.

Enchanting Actions ๐Ÿ’ซ

Once we've found a line that matches our pattern, it's time to tell AWK what to do with it! Here are some actions our wizard can perform :

  • print: This action displays the matching line on your screen .
  • print $2: This enchantment prints only the second field from the matching line. More on fields soon, I promise!
  • { print "Line " NR ": " $0 }: With this powerful spell, we tell AWK to print the line number (NR), followed by a colon and the entire line ($0).

Now it's time to put everything together and create our first AWK spell!

Casting Our First AWK Spell ๐Ÿง™โ€โ™‚๏ธโœจ

Let's say we have a file named fruits.txt that looks like this:


We want to find all lines containing the word "apple." Here's our spell:

awk '/apple/ { print }' fruits.txt

Once we cast this spell, our friendly AWK wizard will search through the file and display any lines containing the word "apple" :


Success! We did it, young explorers!

Fields: AWK's Treasure Map ๐Ÿ—บ๏ธ๐Ÿ’ฐ

Remember how I mentioned fields? Let me explain. In AWK's world, lines of text are like treasure maps, and fields are the steps we follow to find our hidden treasure! Fields are separated by a field separator, which is usually a space or a tab by default.

Let's look at an example. If we have a file called scores.txt with the following content:

Alice 10 20 30
Bob 40 50 60

Here, each line has four fields. For Alice, the first field is "Alice," the second is "10," the third is "20," and the fourth is "30."

Now let's cast a spell that prints only the first and last fields for each line:

awk '{ print $1 " " $NF }' scores.txt

NF is a special symbol in AWK that represents the total number of fields in a line. This spell will show the following output on our screen:

Alice 30
Bob 60

We found our hidden treasure!

AWK's Magical Toolbox ๐Ÿงฐโœจ

AWK comes with a magical toolbox full of built-in functions and variables that we can use in our spells . Here are a few examples:

  • length(): This function returns the length of the given string or the entire line if no string is provided.
  • substr(s, i, n): This enchantment extracts a substring from the string s, starting at position i and with a length of n.
  • split(s, a, fs): With this powerful incantation, we can split the string s into an array a using the field separator fs.

Our journey through AWK's magical world has come to an end, but fear not! There are many more mysteries to uncover, secrets to learn, and spells to master. So grab your wizard hat, and get ready to cast your own AWK spells! is a collection of articles on a variety of technology and programming articles assembled by James Padolsey. Enjoy! And please share! And if you feel like you can donate here so I can create more free content for you.