Yeah, another way to do it is

#!/bin/bash
set -euo pipefail

if [[ $# -lt 1 ]]
then
  echo "Usage: $0 argument1" >&2
  exit 1
fi

i.e. just count arguments. Related, fish has kind of the orthogonal situation here, where you can name arguments in a better way, but there’s no set -u

function foo --argument-names bar
  ...
end

in the end my conclusion is that argument handling in shells is generally bad. Add in historic workarounds like if [ "x" = "x$1" ] and it’s clear shells have always been Shortcut City

Side note: One point I have to award to Perl for using eq/lt/gt/etc for string comparisons and ==/</> for numeric comparisons. In shells it’s reversed for some reason? The absolute state of things when I can point to Perl as an example of something that did it better

Come to think of it, I probably have never done so. Now I’m scared.

I think you mean amanzing.

I’ll see myself out.

Woah, that ((i++)) triggered a memory I forgot about. I spent hours trying to figure out what fucked up my $? one day.

When I finally figured it out: “You’ve got to be kidding me.”

When i fixed with ((++i)): “SERIOUSLY! WTAF Bash!”

From https://mywiki.wooledge.org/BashFAQ/105

Once upon a time, a man with a dirty lab coat and long, uncombed hair showed up at the town police station, demanding to see the chief of police. “I’ve done it!” he exclaimed. “I’ve built the perfect criminal-catching robot!”

The police chief was skeptical, but decided that it might be worth the time to see what the man had invented. Also, he secretly thought, it might be a somewhat unwise move to completely alienate the mad scientist and his army of hunter robots.

So, the man explained to the police chief how his invention could tell the difference between a criminal and law-abiding citizen using a series of heuristics. “It’s especially good at spotting recently escaped prisoners!” he said. “Guaranteed non-lethal restraints!”

Frowning and increasingly skeptical, the police chief nevertheless allowed the man to demonstrate one robot for a week. They decided that the robot should patrol around the jail. Sure enough, there was a jailbreak a few days later, and an inmate digging up through the ground outside of the prison facility was grabbed by the robot and carried back inside the prison.

The surprised police chief allowed the robot to patrol a wider area. The next day, the chief received an angry call from the zookeeper. It seems the robot had cut through the bars of one of the animal cages, grabbed the animal, and delivered it to the prison.

The chief confronted the robot’s inventor, who asked what animal it was. “A zebra,” replied the police chief. The man slapped his head and exclaimed, “Curses! It was fooled by the black and white stripes! I shall have to recalibrate!” And so the man set about rewriting the robot’s code. Black and white stripes would indicate an escaped inmate UNLESS the inmate had more than two legs. Then it should be left alone.

The robot was redeployed with the updated code, and seemed to be operating well enough for a few days. Then on Saturday, a mob of children in soccer clothing, followed by their parents, descended on the police station. After the chaos subsided, the chief was told that the robot had absconded with the referee right in the middle of a soccer game.

Scowling, the chief reported this to the scientist, who performed a second calibration. Black and white stripes would indicate an escaped inmate UNLESS the inmate had more than two legs OR had a whistle on a necklace.

Despite the second calibration, the police chief declared that the robot would no longer be allowed to operate in his town. However, the news of the robot had spread, and requests from many larger cities were pouring in. The inventor made dozens more robots, and shipped them off to eager police stations around the nation. Every time a robot grabbed something that wasn’t an escaped inmate, the scientist was consulted, and the robot was recalibrated.

Unfortunately, the inventor was just one man, and he didn’t have the time or the resources to recalibrate EVERY robot whenever one of them went awry. The robot in Shangri-La was recalibrated not to grab a grave-digger working on a cold winter night while wearing a ski mask, and the robot in Xanadu was recalibrated not to capture a black and white television set that showed a movie about a prison break, and so on. But the robot in Xanadu would still grab grave-diggers with ski masks (which it turns out was not common due to Xanadu’s warmer climate), and the robot in Shangri-La was still a menace to old televisions (of which there were very few, the people of Shangri-La being on the average more wealthy than those of Xanadu).

So, after a few years, there were different revisions of the criminal-catching robot in most of the major cities. In some places, a clever criminal could avoid capture by wearing a whistle on a string around the neck. In others, one would be well-advised not to wear orange clothing in certain rural areas, no matter how close to the Harvest Festival it was, unless one also wore the traditional black triangular eye-paint of the Pumpkin King.

Many people thought, “This is lunacy!” But others thought the robots did more good than harm, all things considered, and so in some places the robots are used, while in other places they are shunned.

The end.

Exercise 6:

set -e
f() { false; echo survived; }
if ! f; then :; fi

That one was fun to learn.

Even with all the jank and unreliability, I think set -e does still have some value as a last resort for preventing unfortunate accidents. As long as you don’t use it for implicit control flow, it usually (exercise 6 notwithstanding) does what it needs to do and fails early when some command unexpectedly returns an error.

“There are still the billion other footguns built directly into bash that will destroy hopes and dreams, but”

That’s well put. I might put that at the start of all of my future comments about bash in the future.

I’m so used to using powershell to handle collections and pipelines that I find I want it for small scripts on Mac. For instance, I was using ffmpeg to alter a collection of files on my Mac recently. I found it super simple to use Powershell to handle the logic. I could have used other tools, but I didn’t find anything about it terrible.

Honestly, the fact that bash exposes low level networking primitives like a TCP socket via /dev/TCP is such a godsend. I’ve written an HTTP client in Bash before when I needed to get some data off of a box that had a fucked up filesystem and only had an emergency shell. I would have been totally fucked without /dev/tcp, so I’m glad things like it exist.

EDIT: oh, the article author is just using netcat, not doing it all in pure bash. That’s a more practical choice, although it’s way less fun and cursed.

EDIT: here’s a webserver written entirely in bash. No netcat, just the /bin/bash binary https://github.com/dzove855/Bash-web-server

For more complicated input/output file handling, certainly.

Little shell scripts do great though if all you need to do is concatenate files by piping them.

It’s like the Internet, it’s not one big truck but a series of tubes.

Nah, it’s in the past.

But people, if you are writing a command that detects a terminal to decide to color its output or not, please add some overriding parameters to it.