htop Interactive Process Viewer

htop is a free and open-source interactive process viewer and system monitor for Unix-like operating systems, providing a real-time, color-coded, terminal-based view of running processes, system resources, and process management capabilities. Originally created by Hisham Muhammad (a Google software engineer and PackageKit contributor, born in Brazil) in 2004 as a more user-friendly alternative to the traditional Unix top command, htop has been maintained by the htop community since 2018. Key features: interactive process management: unlike top which requires typing commands, htop provides a full-screen, menu-driven interface where users can navigate with arrow keys, select processes, and perform actions (kill, renice, trace) using function keys and mouse support. Color-coded display: processes are color-coded by type (green for normal processes, blue for threads, red for kernel threads), and resource bars use colors to differentiate user/system/nice CPU time. CPU visualization: per-core CPU usage bars (not aggregated), with colors indicating user processes (green), system/kernel (red), nice priority (blue), IRQ (magenta), and idle. Memory meters: separate RAM and swap usage bars with color-coded segments for used, buffers, and cache. Process information: PID, user, priority, nice value, virtual memory, resident memory, shared memory, CPU percentage, memory percentage, time, and command. Tree view: hierarchical process view showing parent-child relationships. Sorting: sort by any column (PID, CPU, memory, user, time) with reverse sort. Filtering: filter processes by user or search string (F5/F6). Process actions: kill (F9/k), renice (F7/F8), trace system calls (press l for strace), list open files (press l for lsof). Customizable: user-defined meters, color schemes, display options. F1 help screen. Cross-platform: Linux, FreeBSD, OpenBSD, macOS, Solaris. GPL-2.0.