bash workshop


On two consecutive Sunday evenings (2023-02-26 and 2023-03-05) I hosted the bash workshop on behalf of TechJI.

I am standing in front of a projector screen in an

▲ Me delivering the talky part of the workshop


Despite its name, much of this workshop is not about bash alone, but other tools as well. Here is a brief list:

Part 1

  • Intro
    • Brief history
    • Unix philosophy
  • Files & File Tree
    • cat, cp, mv, rm
    • cd, pwd, ls, mkdir
    • Paths, ., .., *
  • CLI
    • Options and arguments
    • Reading man pages
    • Keyboard shortcuts
  • Pipes
    • stdin, stdout
    • > and >>
    • Pipes
    • grep

Part 2

  • Regex (ERE)
    • Patterns
    • grep -E
    • sed -E 's///'
    • Capturing groups
  • Scripting
    • Variables
    • if
    • for


I've been on Linux for 5 years. It would be a shame if I kept all that bash knowledge to myself. I believe bash is something that every computer-related major student should know, for the following reasons:

  1. Efficiency. Bash has saved hours if not days of my time and will save yours as well.

  2. Portability. Literally every server you may ssh into will have a shell of some sort, and having a hint of how it works will surely help.

Therefore, the aim of bash workshop is

  1. Learn commands/scripts/tricks to boost efficiency

  2. Make the most out of GNU coreutils and a few common tools you'd find anywhere

Materials used

  • Slides (2x, ~50 pages each totalling 1.5k lines of LaTeX)
  • Cheatsheet (A4 sheet handed out on site)
  • Tarball (Follow-along examples and DIY materials)

Participants were asked to download a zip file containing all three.


Work began in October 2022. I scraped together all the topics I feel confident sharing with others, and then kicked out what I felt wasn't common enough. For example tr and cut.

In November 2022 I approached Prof. Manuel Charlemagne with an early draft to ask if he had any advice. The draft was not yet split in half; it was a 71-page giant mess. His advice was to

  • Pack less in one workshop
  • Create fun activities to engage participants
  • Remove that distracting navbar on the bottom

A bar of buttons

▲ Navbar in the default LaTeX beamer theme

I decided that the workshop should follow a practicality-first approach, so I filled the slides with examples that's like, "yeah you'll have to figure this out sooner or later, so I'll show you how right now".

Slide screenshot

▲ Slide in section 5, "Bash Scripting"


Environment variables

Let's say you're downloading something from a completely legal website, and you want the traffic to go through your completely legal local proxy for completely legal reasons.

# set environment variable for local proxy
$ export HTTPS_PROXY=http://localhost:8080/
# download the thing
$ curl -O

I also designed DIY sessions at the end of each section where I ask every participant to run some commands, design a regex, write a script, etc.

Slide screenshot

▲ Challenge session at the end of section 2, "CLI"



  • Read the man page for head
  • Experiment with files in 02-cli/
  • Find a command to generate the following:
==> p0.txt <==
==> p1.txt <==


$ head -n1 -v p0.txt p1.txt

By the way, the navbar can be removed with

\setbeamertemplate{navigation symbols}{}


The cheatsheet is a compilation of commands, regexes and syntax I covered.

Part of cheatsheet

▲ I spent 6 RMB on 30 copies. 13 were handed out on site.

Easter eggs

Slide screenshot

▲ On top of practicality I tried my best to sprinkle some humor.


A brief history of bash

  • Born: 1989
  • Probably played Pokémon on the Game Boy
  • Is an umbrella term for zsh, fish, …
  • Runs on Unix-like environments

Slide screenshot

▲ The final DIY challenge at the very end


The Ultimate Challenge

Each line in 05-scripting/obf.txt begins with an 8-digit number. Print every line with its number greater than any of the lines above.

for line in $(cat obf.txt); do
    num=$(echo $line | grep -oE '^[0-9]{8}')
    if [[ $num -gt $max ]]; then
        echo $line

Now, with so much said and done, be prepared for the best trolling in TechJI's history.

You probably won't be surprised…

ASCII art of Rick Astley


We needed to advertise our event to get people to come. I wrote the first draft on 2023-02-16, which begins with the place, time, topics and prerequisites, followed by the actual marketing.

I ask readers to imagine themselves as an intern who received a message from their boss:

"And here's some simpler work for you… ssh into the server, backup the logs in /var/log, and grep the error codes generated within one minute past each hour, then deduplicate them and…"

The intern panics, for they never touched bash other than the bare minimum to pass VG151. Panic turns into regret — that they failed to show up on our workshop.

And thus the manipulation is done; reader is brainwashed to participate.

(No, of course they aren't.)

Bash workshop: A Quarter Century of Unix

▲ Header banner of WeChat article

Two more revisions finalized the article on 2023-02-22. My venue reservation was approved the next day, but not yet confirmed via email, so I delayed posting.

By Saturday, 2023-02-25, I realized it was Too Fucking Late™ and urgently sent the article anyway. However I was told we can't because WeChat limits our account to only one batch of articles each day, and it's already out there.

(TechJI used to have its own account, but after some reformation all departments share one account, JISU.)

This means we have to advertise for a Sunday event — on Sunday. The article dropped at 10 o'clock.

Lesson learned: never pretend to play safe when you hear the clock ticking.

How it went


# of participants who showed up in person are 10 and 4, respectively, for the two parts.

4 was a bit low but given the abundance of competing events that night (there was an art festival and a guitar concert which, had there been no bash workshop, I would be vibing to). However, this meant a high attention-per-person.


Part 1 lasted around 1.5 hr; part 2 lasted 2.5. Part of the 2.5 was troubleshooting one by one.

In retrospect I should have kicked out sed and capturing groups. This will eliminate one DIY session which I admit is a bit overwhelming for those who heard the word "regex" for the first time.

Unexpected technical problems

  • Accessing WSL filesystem might be tricky in Windows
  • One person trapped themselves in vim
  • bash refuses to execute scripts with \r\n linebreaks
  • On MacBooks, the default bash is FreeBSD flavor and parses {01..05} as {1..5}


Here is a list of things I will fix if I were to do it again.

I will test the scripts on macOS;

I will prepare the promotional article sooner so it gets published at least three days before the event, not nine hours;

I will recap the conventions from part 1 so they don't confuse participants in part 2;

edited xkcd

Original: "Average Familiarity"


Two stick figures have a conversation.

"The command line is second nature to us Linux users, so it's easy to forget that the average person probably only knows how to use coreutils and one or two regexes."

"And tar cvf of course."

"Of course."

Caption: Even when they're trying to compensate for it, experts in anything wildly overestimate the average person's familiarity with their field.

I will clarify where participants should cd into before they run commands;

I will emphasize the difference between:

  • var and $var
  • echo $str and cat file
  • echo $str | COMMAND and COMMAND $str


If workshops were children this would be my firstborn. To build a workshop from scratch is gratifying, especially when the topic is an extract of my five years of experience. I would like to thank Prof. Manuel Charlemagne; the feedback was very useful.

I learned how to weigh things — to tell things that matter from those that don't — and how to make it worth the time for both friends and strangers.

However, I need to rework my strategy toward event preparation. I should have pushed forward more aggressively. Few problems are worse than running out of time. There was no need to play safe.

$ ~ exit