Tools: From Curiosity to Code: How I Built SysLens, a Linux CLI System Monitor

Ever wondered what’s really happening inside your Linux system? The tools you use every day—top, htop, neofetch—give you the numbers, but do you know how they actually work under the hood? I didn’t—so I decided to build my own. Enter SysLens: a lightweight, fast, and simple CLI system monitor written entirely in C. Why Another System Monitor? There are dozens of Linux tools already. Why make one more? For me, it was all about learning by doing. Every new project is a skill test, and building something from scratch forces you to explore details you’d otherwise take for granted. With SysLens, I wanted to: Understand the Linux /proc filesystem deeply Parse and display system stats efficiently in C Learn to build a professional, modular CLI tool SysLens gives you essential system information in a clean, readable format: [ System Info ]
OS : Ubuntu 22.04 | Kernel : 6.8.0
CPU : Intel(R) Core(TM) i5
Uptime : 27 mins | User : mahmudul [ Resource Usage ]
RAM : [###.......] 34% (2.7GiB/7.6GiB)
Swap : [..........] 0%
Load avg : 1.40, 1.17, 0.78 [ Active Processes ]
Task : 231 total | 2 running | 229 sleeping | 0 zombie No clutter. No fluff. Just real-time, critical system info at a glance. System Overview: OS, Kernel, CPU, uptime, current user Resource Monitoring: RAM, swap, load averages with color-coded bars Process Stats: Total, running, sleeping, and zombie processes CLI Flags: -s, -m, -p, --help, --version Lightweight & Fast: Minimal memory footprint, no external dependencies SysLens reads directly from Linux’s virtual /proc filesystem: /proc/cpuinfo → CPU model /proc/meminfo → RAM and swap usage /proc/loadavg → system load averages /proc/uptime → uptime /proc/[PID]/status → process states By parsing these files safely and efficiently, it outputs everything you need without unnecessary overhead. I kept the code modular to maintain readability and scalability: syslens/
├── include/main.h # Headers & macros
├── src/main.c # CLI & orchestrator
├── src/sys.c # OS & CPU info
├── src/mem.c # Memory & load logic
├── src/proc.c # Process parsing
├── Makefile
└── README.md Every module handles a single responsibility—classic separation-of-concerns in action. Building SysLens taught me more about Linux internals than I could have imagined: How virtual filesystems expose kernel data How to parse system stats safely and efficiently How to design CLI tools with modular C code The importance of readable, maintainable code The best way to learn a tool is to build it yourself. Real-time CPU usage bars Disk and network monitoring Automated builds and CI/CD pipeline for multi-platform releases GitHub: https://github.com/mahmudul626/syslens
Portfolio: https://mahmudul.pro.bd Just clone, make, and run: git clone https://github.com/mahmudul626/syslens.git
cd syslens
make
./syslens SysLens started as a curiosity experiment, but now it’s a full-fledged CLI tool. If you’re a Linux developer or C programmer, I challenge you to build one of the tools you use every day. It’s an incredible way to level up your skills and truly understand your system. Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. Hide child comments as well For further actions, you may consider blocking this person and/or reporting abuse - Understand the Linux /proc filesystem deeply
- Parse and display system stats efficiently in C
- Learn to build a professional, modular CLI tool