In Praise of Small Shell Scripts

code bash ..... January 18, 2024

Later: Making A Tiny E-Paper Status Display for the Raspberry Pi Zero
Earlier: 2024 Blogging Intentions

Over the decades I've relied heavily on bash aliases and functions to automate common tasks, resulting in a .bash_profile that's over a thousand lines long. But lately I find myself writing many small scripts instead.

These tiny scripts, which live in a directory on my $PATH, have several advantages:

• They compose nicely, in line with the Unix philosophy.
• They are reasonably portable. If it works for me on Linux, it'll often work on my Mac, and vice versa.
• They start quickly and are often as fast as something you'd write in Python, Ruby, etc.
• Their file creation / modification times are distinct and provide a history of what you worked on, when; by contrast, everything in .bash_profile is muddied together.
• They run in subprocesses without needing to get your .bash_profile involved (helpful for Org Babel or any situation where you need to run your script from another program).

Even something as trivial as an alias might get its own shell script, if I can give it a name that's easier to remember than the original program name or combination of arguments. Bash is an awkward language for doing complex things, but expressive enough for simple tasks. And ChatGPT or other AI tools can often write simple scripts correctly for you with little or no modification.

Here are some examples of small scripts I've been using recently:

• ghjobs : Show status of my active CI jobs on GitHub (wrapper around gh tool); avoids having to go to the Web site, usable inside watch, etc.
• inprog / ondeck : Show GitHub issues tagged as "in progress" or "on deck," across all my "work" repositories;
• (several programs) : Run one of many different build variants on the embedded system I'm working on (build for Mac, build for target hardware, build with fast tests, build all variants prior to pushing code, etc.);
• (several programs) : Select random figurative references for inspiration or to draw from (there are many variations of this one);
• bashscript : Create a new bash script in the appropriate place (on $PATH).

This last one is simple and helpful enough to show here:

#!/bin/bash

script_name=$1

cat << EOF > ~/bin/$script_name
#!/bin/bash

echo "OK"
EOF

chmod +x ~/bin/$script_name

Bash is boring and old (I still have csh scripts from more than 30 years ago; csh is a close cousin of bash). It's also everywhere – on my Mac, inside my Docker containers, on my Raspberry Pi's, on my client's servers, and on the cloud VMs I work on.

The "many small scripts" approach is complementary to how I use make, which I wrote about previously.

Finally, here's the small script I wrote yesterday to hopefully get me writing more often:

#!/bin/bash

BLOGHOME=${BLOGHOME:-$HOME/Docs/websites/johnj22}

cd $BLOGHOME
pwd

echo -n "Title for post: "; read title
postdate=$(date '+%Y-%m-%d')
echo $title $postdate

# Turn the title lower case/kebab case, remove extra characters.  Thanks, ChatGPT!
title_kebab=$(echo "$title" |
              tr '[:upper:]' '[:lower:]' |
              tr -s '[:space:]' '-' |
              sed 's/[^a-z0-9-]//g; s/^-//; s/-$//')

echo -n "$title" | pbcopy

file="content/posts/$title_kebab"".org"

if [ ! -e $file ]; then
    cat <<EOF > $file
---
title: $title
date: $postdate
draft: true
tags:
---
# Org Mode stuff in case I export the document on its own without using Hugo:
#+OPTIONS: toc:nil num:nil

EOF

fi

ae $file  # `ae` is another small script: loads the resulting file in Emacs.

Typing "newpost" asks me for a title and pops me in my editor with all the boilerplate needed to get me on my way. Nice and easy.

Later: Making A Tiny E-Paper Status Display for the Raspberry Pi Zero
Earlier: 2024 Blogging Intentions