Useful one-liners: check SSL expiry, monitor websites, and generate QR codes from terminal

Some handy CLI tricks:

Check SSL certificate expiry:

 bash

    
echo | openssl s_client -connect example.com:443 2>/dev/null | openssl x509 -noout -dates

  

Monitor a webpage for changes:

 bash

    
watch -d -n 300 "curl -s https://example.com/ | md5sum"

  

Generate a QR code from terminal:

 bash

    
qrencode -t UTF8 "https://your-url.com/"

  

Quick JSON formatting:

 bash

    
echo "{\"key\":\"value\"}" | python3 -m json.tool

  

Decode a JWT token:

 bash

    
echo "your.jwt.token" | cut -d. -f2 | base64 -d 2>/dev/null | jq .

  

If you want these as quick web tools (useful when SSHd into a box without these packages), I threw together a free API toolkit that does all of this over HTTP: JSON formatting, JWT decoding, QR generation, UUID gen, hashing, etc.

What are your go-to one-liners?

OC by @devtoolkit_api@discuss.tchncs.de