The UNIX Programming Environment - by Brian W. Kernighan & Rob Pike

This book, published in 1984, is a guide to the philosophy and practice of UNIX. It emphasizes modularity, simplicity, and the “toolbox” approach: small programs that do one task well, combined through pipes and scripts. The authors introduce shell programming, text processing tools (sed, awk, grep), and file handling, illustrating how UNIX encourages experimentation and productivity. Though some technical details are dated, its central message—clarity, reusability, and composability in software design—remains influential.