strace attaches to a running Linux process and prints every system call it makes, in real time: every file it opens, every network connection it attempts, every byte it reads, every signal it receives. It is invaluable for debugging programs that refuse to explain why they’re failing, and mildly alarming for revealing what your software actually does when you’re not looking. Running strace on a freshly launched application and watching it frantically read dozens of config files, probe nonexistent library paths, and rattle doorknobs across the filesystem is a reliable cure for any lingering faith in software quality. strace was invented in 1992. There has been no shortage of material since.
