Explainer
Can you recover a private key from an Nginx certificate?
A certificate cannot reveal its matching private key. Locate a saved key, verify the public-key match, or generate a new key and reissue.
Technical guide
Generate a self-signed TLS certificate with OpenSSL
Create a SAN-bearing test certificate with OpenSSL 3.x, protect the private key, and understand the separate requirement for client trust.
Explainer
Get the class name of a Python instance
Use type(obj).__name__ for an instance’s class name, and add the module and qualified name when a short name is ambiguous.
Explainer
Email cron job errors with MAILTO
Configure cron mail delivery and use an exit-status wrapper when you need messages only for failed runs.
Explainer
Get the current date and time in Python
Read local or UTC time with datetime, obtain Unix timestamps, and use an elapsed-time clock when measuring how long code runs.
Explainer
Exclude selected container logs from Filebeat
Filter container logs by file path, enriched metadata, or Kubernetes autodiscover rules using filestream inputs.
Explainer
Get the last element of a Python list
Read a list’s final item with negative indexing, handle empty lists deliberately, and distinguish reading an item from removing it.
Explainer
Get the length of a Python list
Use len() to count list elements, understand what nested lists count, and handle iterators that do not provide a length.
Technical guide
List files in a directory with Node.js
Read entry names with readdir, filter Dirent objects by type, or walk incrementally when directory size and symlink behavior matter.
Technical guide
Get the current module’s path in Node.js
Use CommonJS filename variables or ES module metadata, and distinguish a module’s location from the process working directory.
Technical guide
Combine a certificate and private key into a PEM file
Combine PEM-encoded certificate and key files safely, preserve certificate-chain order, and validate the resulting bundle for its target service.
Explainer
Extract a substring in Python
Use string slices for index ranges, handle delimiters safely, and account for negative indexes, zero-length requests, and Unicode boundaries.