The free command—along with ps, top, kill, pgrep, and dozens of other system utilities—is maintained as part of the procps-ng project. Source repository The source code is hosted at: https://gitlab.com/procps-ng/procps You can clone it with: git clone https://gitlab.com/procps-ng/procps.git cd procps Most distributions package procps-ng, so you likely already have it installed. You can verify the…
When you open a popup window with window.open(), you’ll often need to detect when the user closes it so you can update your UI, refresh data, or clean up resources. Here are the practical approaches, from polling to event-driven methods. Polling the closed property The simplest method is to periodically check the popup’s closed property:…
Sending POST requests from client-side JavaScript is a common task, and you have several modern options. The approach you choose depends on your project’s dependencies and browser support requirements. Fetch API (Recommended for Modern Projects) The Fetch API is the modern standard and requires no external library. It’s built into all current browsers and handles…
When troubleshooting wireless performance, you need to know both the negotiated link speed and actual throughput. ethtool won’t help here — it’s for wired interfaces. For wireless adapters, you’ll need different tools depending on what information you’re after. Using iwconfig for link speed The iwconfig command shows the currently negotiated link rate between your adapter…
The x86-64 ISA provides ucomiss and ucomisd for comparing SSE floating-point values. These instructions compute S1 – S2 and set the EFLAGS register (ZF, PF, CF) based on the result. Instruction Operands Purpose ucomiss S2, S1 Compare single-precision (32-bit) floats ucomisd S2, S1 Compare double-precision (64-bit) floats In AT&T syntax, the source operand is listed…
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…
When a process receives a signal from kill or pkill, it needs a signal handler to intercept and respond to it. Without one, most signals terminate the process immediately. This guide covers setting up robust signal handlers for production daemons. Understanding Signals The kill command sends signals to processes. By default, it sends SIGTERM (signal…
When debugging a program or understanding what it actually touches on your filesystem, you need to see which files it opens. Two tools do this well: strace traces system calls in real time, while lsof inspects a running process without the overhead. Using strace to capture file operations The simplest approach is to run strace…
WhatsApp dominates global messaging, but several strong alternatives exist depending on your use case, privacy requirements, and regional adoption. Here’s what’s actually worth considering in 2026. Messaging Apps Built for Mobile Signal The gold standard for privacy-conscious users. Signal uses end-to-end encryption by default for all messages, calls, and group chats. Open source, no ads,…
Sending sensitive information via email requires careful consideration. Whether you’re sharing financial details, credentials, or confidential documents, there’s no single “secure email” solution that eliminates all risk — you need to match the method to your threat model. Understand the Risk Standard email transmits in plaintext across multiple servers. Even with TLS in transit, your…
Handling Ctrl-C gracefully in a Bash script is essential when you need to perform cleanup operations, save state, or notify users before exiting. The trap builtin makes this straightforward. Basic Trap Setup The fundamental approach uses the trap command to catch the INT signal (which Ctrl-C generates): trap ctrl_c INT function ctrl_c() { echo “Ctrl-C…
Y-axis labels in Gnuplot can end up positioned awkwardly depending on your terminal, font, and tick label width. The most straightforward solution is using the offset option in the set ylabel command. Basic Offset Syntax The offset takes three parameters: horizontal, vertical, and depth (for 3D plots): set ylabel “Y Label” offset <x_offset>,<y_offset>,<z_offset> Positive values…
This post addresses a fair question: with Stack Overflow, Reddit, and countless other Q&A platforms already established, why create a dedicated Q&A space? There are three practical reasons. Short-form technical tips Some knowledge doesn’t warrant a full blog post. A 2000-word article dilutes what should be a focused tip. Q&A format works better for these…
The x86-64 architecture on Linux follows the System V AMD64 ABI calling convention. Understanding this is essential when writing assembly, optimizing code, debugging, or interfacing with C libraries. Register usage for arguments Integer and pointer arguments use these registers in order: RDI — first argument RSI — second argument RDX — third argument RCX —…
Data visualization transforms raw metrics into actionable insights. When you’re managing infrastructure metrics, application logs, business KPIs, or system performance data, visualization is how you extract signal from noise. The human brain processes visual information faster and more reliably than log files or spreadsheet rows—which is why dashboards have become essential infrastructure in modern operations….
Quartz is an open-source Java library for scheduling background jobs and tasks. Whether you need to execute work at specific times, on recurring intervals, or in response to events, Quartz provides a robust scheduling framework that integrates with standalone applications, application servers, and clustered environments. Core Features Embeds directly into standalone or web applications Supports…
The traditional fork-exec pattern works, but it’s error-prone. posix_spawn() handles process creation in a single call with several advantages: Atomic operation: Spawn and exec happen atomically, eliminating race conditions between fork and exec No fork quirks: You don’t need conditional logic for parent vs. child code paths — exec happens immediately in the child Direct…
Programs need to shut down gracefully—saving state, closing connections, flushing buffers—rather than terminating abruptly. A daemon might receive a termination signal and need to persist in-memory data before exiting. The challenge is catching these signals in C and responding appropriately. Signal basics The kill command sends SIGTERM by default. This signal is catchable and allows…
Measuring time accurately matters for performance profiling, benchmarking, and latency-sensitive applications. Linux provides several APIs with different tradeoffs in resolution, overhead, and reliability. Understanding which to use prevents subtle bugs in production code. POSIX Time APIs: gettimeofday and clock_gettime gettimeofday() and clock_gettime() are the standard POSIX calls for reading system time. gettimeofday() returns seconds and…
ASCII stands for American Standard Code for Information Interchange. It’s a 7-bit character encoding standard mapping numeric values (0-127) to printable characters and control codes. Since computers work with numbers at the lowest level, ASCII provides a universal way to represent text—each character has a unique numeric value. Standardized in 1963, ASCII remains foundational to…