Shing Lyu

Generating a notification sound in command-line

You want to play a notification sound in a Linux shell script, but don’t want to download any sound files (e.g. MP3, WAV, MIDI). Here is a script that generates the sound on-the-fly:

First install SoX, the Swiss Army knife of sound processing programs.

sudo apt-get install sox

Then:

play -n synth 0.3 pluck A3 vol -20dB repeat 2

• play: the player command from SoX.
• -n: Play a “null file”.
• synth 0.3 pluck A3: Play the A3 (220.00 Hz) sound for 0.3 seconds, with a waveform that simulates a guitar string pluck.
• vol -20dB: The default is too loud, reduce the volume by -20dB.
• repeat 2: Repeat twice (i.e., total 3 times).

How to import serde's custom derive macors properly?

TL;DR Follow the official documentation

Caveats in Terraforming WAF V2 for CloudFront

If you want to add a WAF V2 (aws_wafv2_web_acl) to a CloudFront distribution (aws_cloudfront_distribution) using Terraform, there are a few caveats:

Check MongoDB index usage statistics

Run this command to get the usage of each index:

RFC2616 is dead, read RFC723X

While looking for the definition of HTTP Status Codes, I realize that RFC2616 is deprecated. You should look for RFC7231 instead.