Using AWK to extract generated file from jekyll-compose

Recently, I have been using jekyll to make notes. I use jekyll-compose gem to create post using command line. However, the auto open generated file features isn’t working in my machine after the setup.

After a few times on manually opening the generated files in vim, I decided to write a quick shell script to solve this issue.

Scenario

To generate a new post with jekyll-compose, we can run the following command:

bundle exec jekyll post <TITLE>

and it will output the following:

Configuration file: /Users/kai/Desktop/notes/_config.yml
New post created at _posts/<DATE>-<TITLE>

So, to generate and open the file involves the following steps:

• Run the command to generate post
• Extract the file path
• Open the file using vim

awk

I came across AWK from Julia Evans zine. It came to my mind again when I want to extract the file path from the output of the command.

AWK is a programming language designed for text-processing. It has very basic yet important command print to output the text. What makes AWK different is it breaks each line into columns (seperated by space, which can be configure), where:

print $1

means output the first column.

We can also add in a specific condition in front of the print command so that it only execute if the condition is true.

CONDITION {print $1}

Implementation

After knowing some basic of AWK, we can extract the file path with the following actions.

1. Extraction

Hence, to extract out the file path from the line New post created at _posts/<DATE>-<TITLE>, we can use the following command:

echo 'New post created at _posts/<DATE>-<TITLE>' | awk '{print $5}'

$5 is used since the file path is the fifth column of the line.

2. Only Extract Second Line

Since we just wanted to extract the second line of the command output, the command above is not enough. What we really wanted is to say:

if the line is second row, then we extract it

To achieve that in AWK, we can use AWK built-in variables FNR, which refers to the current line number of the file, to form a condition.

echo -e "Configuration file: /Users/kai/Desktop/notes/_config.yml\nNew post created at _posts/<DATE>-<TITLE>" | awk 'FNR==2{ print $5 }'

Summary

1. You can use AWK to print specific column of lines with awk {print $N}
2. You can add condition in front of the print command if needed.
3. AWK contains a handful of built-in variables that are useful for text-processing.
4. Code snippet to generate and open the file.

function newpost() {
  vim $(
    bundle exec jekyll post $1 |
    # substr is used to remove the ending '.' of the extracted string
    awk 'FNR == 2{print substr($5, 1, length($5) - 1)}'
  )
}

1. If you are interested in more command line tools, you can consider purchase Julia Evans Byte Size Command Line zine series.

2. It turns out the reason why my jekyll-compose configuration doesn’t work is because of a single typo of -. Instead of:

# The correct one
jekyll_compose:
  auto_open: true

I use:

# The wrong one
jekyll-compose:
  auto_open: true