nickjj / lcurl

Visit a site every X seconds in a loop to help detect downtime while testing deployment strategies.

What is lcurl?

It's a Bash script (yep it uses Bash features) that runs a specific curl command X number of times in a loop. It will report back the HTTP status code, how long it took to get a response, a timestamp and the loop count.

Here's an example of visiting https://example.com every 250ms for a max of 5 times:

lcurl https://example.com 0.25 5

Running the above command will produce this output:

200 | 0.069927s | 2021-12-11T08:47:00 | 1/5
200 | 0.063947s | 2021-12-11T08:47:00 | 2/5
200 | 0.060945s | 2021-12-11T08:47:01 | 3/5
200 | 0.068982s | 2021-12-11T08:47:01 | 4/5
200 | 0.066179s | 2021-12-11T08:47:01 | 5/5

If you omit the max number of times it will run 999999 times by default. The URL and delay (in seconds) are required.

Demo Video

This video covers why I created the script, using it, installing it and how it's implemented using a bit of shell scripting.

Installation

Since this script uses curl you'll need to have curl installed beforehand. It's available with most package managers depending on your OS. For example you can apt, brew, pacman or yum install curl.

Then all you have to do is download this lcurl script, make sure it's executable and place it somewhere on your system path.

1 liner to get lcurl downloaded to /usr/local/bin:

sudo curl \
  -L https://raw.githubusercontent.com/nickjj/lcurl/0.1.0/lcurl \
  -o /usr/local/bin/lcurl && sudo chmod +x /usr/local/bin/lcurl

That will download the latest release. If you want to download the bleeding edge version you can replace the version number with main in the above command.

Confirm it works by running lcurl. You'll be greeted with a help menu that shows an example on how to use it.

FAQ

When would you use this script?

This could be useful to help make sure you're able to perform zero downtime deployments of your application. As you roll-out a new version of your app you can use this script to hit your site to make sure it always responds back with 200s. That's the exact use case of why I created this script but I'm sure there's other use cases that you can use this for too.

When wouldn't you use this script?

If you want to get high precision benchmarks or are profiling an application there are much better tools for this such as wrk. lcurl reports back how long it took to receive a response but that's mainly because "why not". It's nice to have and it took about a minute to implement because it's a value that's provided by curl.

Why did you name the script lcurl and not curll?

I didn't want TAB completing curl to give you the option of running this script because let's be real now, most of the time if you type out cur your intent is to run curl not this script.

About the Author

I'm a self taught developer and have been freelancing for the last ~20 years. You can read about everything I've learned along the way on my site at https://nickjanetakis.com. There's hundreds of blog posts and a couple of video courses on web development and deployment topics. I also have a podcast where I talk to folks about running web apps in production.