# Daily Hack #day21 - AWK

The `awk` command is a powerful text processing tool that's perfect for manipulating data files in Unix environments. Here are some useful tricks and hacks with awk:

File called `data.txt` contents:
```data.txt
banana, apple, avocado
orange, grapes, tomato
spinach, carrots, banana
orange, garlic, pear
```

Field Extraction:
-----------------

This prints the first, second and third field of each line in the file.

```
awk '{print $1}' data.txt
```
> output:
```
 banana,
 orange,
 spinach,
 orange
```

```
awk '{print $2}' data.txt
```
> output:
 ```
 apple,
 grapes,
 carrots,
 garlic
```

```
awk '{print $3}' data.txt
```
> output:
 ```
 avocado
 tomato
 banana
 pear
```


Field Separator:
-----------------
```
awk -F',' '{print $1}' data.txt
```

>output:
```
 banana
 orange
 spinach
 orange
```

```
awk -F',' '{print $2}' data.txt
```
>output:
```
 apple
 grapes
 carrots
 garlic
```

This sets the field separator to en empty space (',') and prints the first field of each line. Due to the nature of our simple `data.txt` file, it has the same outcome as the first example bit without actually printing the comma.

Replacing Text:
---------------

```
awk '{gsub("banana", "berry", $0); print $0}' data.txt
```
>output:
```
 berry, apple, avocado
 orange, grapes, tomato
 spinach, carrots, berry
 orange, garlic, pear
```

This replaces all occurrences of the old value `banana` with the new value `berry` in each line and prints the modified lines.

Counting Lines:
----------------
```
awk 'END {print NR}' data.txt
```

>output:
```
 4
```

Unique Values:
----------------

Find out how many unique values are there in the first column.
```
awk -F, 'NR>0{print $1}' data.txt | sort | uniq | wc -l
```

>output:
```
 3
```

Find out how many unique values are there in the second column.
```
awk -F, 'NR>0{print $2}' data.txt | sort | uniq | wc -l
```

>output:
```
 4
```

These are just 4 simple examples of what the `awk` command can do. It's a versatile tool with a lot of potential for text processing tasks.