When you need to execute a system command and capture its output in C, popen() is the standard approach. Unlike system(), which just runs a command, popen() gives you a file stream connected to the command’s stdout or stdin. Basic Usage The popen() function signature is: FILE *popen(const char *command, const char *type); The type…
When a program appends data to a file, you need to know how much space remains on the partition containing that file. This determines whether the file can grow or if you’re about to hit a capacity limit. Quick answer To find available space for a file, use df: df -B1 /mnt/logs/app-log.log | tail -1…
When you need to format an integer with leading zeros in bash, printf is the standard approach. This is useful for generating zero-padded IDs, filenames, or any formatted output. Using printf The basic syntax mirrors C’s sprintf: n=42 str=$(printf “%08d” “$n”) echo “$str” # Output: 00000042 Here, %08d means: %d — format as decimal integer…
You have several options for converting HTML files to plain text, each with different strengths depending on your use case. html2text The most straightforward tool is html2text, available on most distributions: html2text input.html The converted text prints to stdout. Redirect to a file if needed: html2text input.html > output.txt Install it via your package manager:…
Converting LaTeX documents to HTML is useful for web publishing. Two main tools handle this conversion effectively: htlatex and latex2html. Both produce valid HTML output, though they have different strengths and limitations. Using htlatex htlatex is part of the tex4ht package and is generally more robust for modern LaTeX documents. Installation: On Fedora/RHEL: sudo dnf…
A hard reset (also called a force restart) clears the device’s RAM and stops any stuck processes without erasing your content or Amazon account data. It’s the first troubleshooting step for freezing, unresponsive screens, or software glitches. Basic Hard Reset Steps Locate the power button on your device (usually on the bottom edge or side,…
LightDM is a lighter alternative to GDM (GNOME Display Manager). If GDM is causing issues, you prefer a simpler login screen, or you’re running a lightweight desktop environment, here’s how to switch to LightDM on Fedora. Install LightDM sudo dnf install lightdm lightdm-gtk-greeter The lightdm-gtk-greeter provides the graphical login screen. Other greeter options include: lightdm-gtk-greeter…
The Unix epoch (January 1, 1970 00:00:00 UTC) is the standard reference point for timestamps across Linux systems. When you need to convert a timestamp like 1349361711.169942 into a readable date, the date command is your primary tool. Basic Conversion The simplest approach uses date with the @ prefix: date -d @1349361711.169942 Output: Thu Oct…
By default, ibus isn’t automatically started on Fedora with Cinnamon. You might try launching the daemon manually: ibus-daemon This starts the ibus service and adds an icon to your system tray, but you’ll find that Chinese input doesn’t work even when enabled through the tray icon. The missing piece is integration with Cinnamon’s input method…
Cinnamon is a modern, feature-rich desktop environment forked from GNOME. It’s lightweight compared to full GNOME installations and offers a traditional taskbar-based interface. Installing it on Fedora is straightforward. Basic Installation Use dnf (the modern package manager) with group install: sudo dnf groupinstall ‘Cinnamon Desktop’ This installs the complete Cinnamon desktop environment along with necessary…
You sometimes need to know whether your shell is running inside screen or tmux. The most straightforward approach is checking the TERM environment variable. Using TERM When screen starts a shell, it sets TERM=screen by default: [user@host ~]$ echo $TERM screen Compare this to a normal terminal session: [user@host ~]$ echo $TERM xterm-256color The TERM…
If you need to remove excess white space or trim margins from PDF files, several graphical tools can handle this on Linux. Here are the most practical options. Krop Krop is a straightforward tool specifically designed for PDF cropping. It lets you define crop regions visually and apply them to single pages or entire documents….
Counting page views isn’t as simple as incrementing a counter. You need to handle edge cases: duplicate views from the same user, multiple users behind a single IP (corporate networks), and bots. Here’s how to build a robust system. The Problem with IP-Based Counting Relying on IP addresses fails in several scenarios: Multiple users behind…
When you need to store form submissions where different form types have different attributes, you’re essentially implementing an Entity-Attribute-Value (EAV) model. This is a common pattern for flexible schemas, but it requires careful design. The Core Problem You have multiple form types (Laptop, Mobile, Tablet) with different fields. A naive approach is a wide table…
When you start a VNC server with the -geometry flag under GNOME 3, you’ll notice the display resolution doesn’t match what you specified: vncserver -geometry 1024×768 This works fine with GNOME 2 and window managers like twm, but GNOME 3 ignores the setting. The actual resolution will be whatever was last used in that session,…
Amazon’s Kindle Library web interface forces you to delete books one at a time through the UI. If you’ve accumulated hundreds of items, this becomes tedious. Here are practical approaches to bulk-delete from your Kindle Library. Browser Console Method The most straightforward approach uses your browser’s developer console to run deletion scripts directly against Amazon’s…
Java Runtime Environment (JRE) is required to run Java applications on Linux. On x86-64 systems, you have several installation options ranging from open-source to Oracle’s commercial builds. Install OpenJDK (Recommended) OpenJDK is the open-source implementation and is available in all major Linux distributions: # Fedora / RHEL / Rocky Linux sudo dnf install java-17-openjdk #…
Start by compiling your C source files into object files: gcc -c lib1.c lib2.c This produces lib1.o and lib2.o. You can use any compiler flags here—-Wall, -O2, -fPIC, etc.—that match your build requirements. Position-independent code (-fPIC) isn’t strictly required for static libraries but is good practice if you anticipate reusing these objects elsewhere. Creating the…
Working with environment variables in C is straightforward using POSIX APIs. The two primary functions are getenv() for retrieval and setenv() for modification. Getting Environment Variables Use getenv() to read an environment variable: #include <stdlib.h> #include <stdio.h> int main(void) { const char *path = getenv(“PATH”); if (path != NULL) { printf(“PATH: %s\n”, path); } else…
[md] Use setenv to set an environment variable in csh: setenv VARIABLE value Replace VARIABLE with the name of the variable and value with its value. The variable is immediately available in the current shell and inherited by child processes. ## Examples Set a simple variable: setenv PATH /usr/local/bin:/usr/bin:/bin setenv EDITOR vim setenv JAVA_HOME /usr/lib/jvm/java-17-openjdk…