Environment variables are essential for configuration management—API keys, database URLs, feature flags, and environment-specific settings should never be hardcoded. Python provides straightforward mechanisms to access them. The os Module The standard way to read environment variables is with the os module: import os api_key = os.environ[‘API_KEY’] This raises a KeyError if the variable doesn’t exist….
The most straightforward way to read an environment variable in Python is with os.getenv(): import os api_key = os.getenv(‘API_KEY’) print(api_key) If the variable doesn’t exist, getenv() returns None. You can provide a default value as a fallback: debug_mode = os.getenv(‘DEBUG’, ‘False’) port = os.getenv(‘PORT’, ‘8000’) For variables that must exist, use os.environ[] instead. This raises…
Getting kernel function call stacks is essential for debugging driver issues, understanding kernel behavior, and performance profiling. The approach depends on what you’re trying to trace: live kernel execution, crash analysis, or post-mortem inspection. Using ftrace The kernel’s built-in ftrace framework is the first tool to reach for. It’s zero-overhead when disabled and has minimal…
VM exits occur when a guest VM transitions to hypervisor mode to handle privileged operations, I/O requests, or other events. Tracking exit counts and types helps identify performance bottlenecks, inefficient guest behavior, and hypervisor overhead. Quick Exit Statistics The debugfs interface provides a simple view of exit counts: cat /sys/kernel/debug/kvm/exits This shows aggregate exit counts…
Error handling is fundamental to Go development. Often you’ll need to convert an error to a string for logging, displaying to users, or including in API responses. Go provides several straightforward approaches. Using the Error() Method Every error in Go implements the error interface, which has a single method: Error() string. The simplest conversion is…
If you’ve set up passwordless SSH login with key-based authentication but lftp keeps prompting for a password, you need to explicitly configure it to use your SSH keys. The basic approach The simplest method is to pass an empty password to lftp, which signals it to fall back on SSH key authentication: lftp -u user,…
Webpages often render differently when printed than on screen. Firefox’s developer tools make it straightforward to preview and debug print stylesheets without wasting paper. Using the CSS Media Type Emulator The fastest way to test print styles in Firefox: Open DevTools with F12 Click the Inspector tab (usually open by default) Look for the “Emulate…
When you run journalctl without options on a system with years of log history, it can take seconds or even minutes to parse everything. The slowness comes from journalctl loading and deserializing potentially gigabytes of journal data. The solution is targeted querying — you almost never need the entire journal, so restrict what journalctl reads…
The TP-LINK T2U is a USB WiFi adapter based on the MediaTek MT7650U chipset. While Linux kernel support has improved significantly, you may still need to manually compile drivers on some distributions. This guide covers installation on modern Fedora and RHEL-based systems. Check if your adapter is already supported First, plug in the adapter and…
Vim is fast by default, but plugins can introduce noticeable lag during startup or while editing. Finding the culprit requires systematic profiling of both startup time and runtime behavior. Profile Vim startup time The quickest way to identify slow plugins is to measure how long Vim takes to initialize: vim –startuptime profile.log This creates a…
When you export a variable in Bash, it becomes available to all child processes spawned from your shell. Sometimes you need to remove that exported status or delete the variable entirely. There are two main approaches depending on what you want to achieve. Remove export status but keep the variable If you want the variable…
Chrome on Linux sometimes fails to start with the error “Your profile could not be opened correctly.” This typically happens when the browser’s profile database becomes corrupted, often after a crash or unclean shutdown. Quick Fix: Remove Corrupted Web Data The most reliable solution is to delete the corrupted Web Data file from your Chrome…
The simplest approach is passing log level flags directly to sbt: sbt –error “compile” sbt –warn “clean compile” sbt –info “test” sbt –debug “publishLocal” Common log level flags: –error — errors only –warn — warnings and errors (default) –info — info, warnings, and errors –debug — verbose debugging output –trace — most verbose, rarely needed…
The standard way to generate patches from git commits is git format-patch. This creates email-ready patch files that include commit messages, author information, and metadata. # Create a patch from the last commit git format-patch -1 # Create patches for the last N commits git format-patch -3 # Create patches from a specific commit onwards…
Direct assignment to window.onload overwrites any existing handler. If a plugin, library, or another script has already set a handler, your code will replace it completely: // Plugin sets this window.onload = function() { initializePlugin(); } // Your code overwrites it window.onload = function() { doMyWork(); } // Result: initializePlugin() never runs This breaks plugins…
When network interfaces fail or behave unexpectedly, you need to inspect driver details, hardware state, and kernel messages. Here’s the practical toolkit for diagnosing network hardware and driver issues. Kernel Messages and Logs Start by checking kernel logs where driver initialization and errors are recorded: dmesg | grep -i network dmesg | grep -i driver…
Bash doesn’t have a goto statement, and that’s intentional. The language is designed to encourage cleaner control flow patterns that are easier to debug and maintain. When you feel the urge to jump around in your script, there’s almost always a better approach. Functions and Early Return The cleanest pattern is extracting logic into functions…
The TP-Link TL-WN725N v2 uses the Realtek RTL8188EU chipset. While kernel support has improved significantly, you may still need to compile drivers manually on recent Fedora releases. Check current driver status First, verify whether your adapter is recognized: lsusb | grep -i realtek If nothing appears, the driver isn’t loaded. Check if the kernel module…
When your OCaml program crashes with Fatal error: Exception “Stack_overflow” but doesn’t tell you where the problem originated, you need to enable backtrace reporting. The process is straightforward but requires recompilation. Enable Debug Symbols and Backtraces First, recompile your program with the -g flag to include debug information: ocamlopt -g -o myprogram myprogram.ml If you’re…
To enable debugging, configure your CMake build with CMAKE_BUILD_TYPE set to Debug. This tells CMake to invoke the compiler with the -g flag, generating debug symbols that tools like gdb and lldb need. From your project’s root directory: cmake -DCMAKE_BUILD_TYPE=Debug -B build cd build make The -B build flag creates a separate build directory, which…