Pro Bash Learn to Script and Program the GNULinux Shell - Third Edition (Jayant Varma, Chris F. A. Johnson) (Z-Library)

【One-Line Pitch】 A practical, idiom-focused guide to treating Bash as a full programming language rather than a command glue layer, updated for Bash 5.2. Best for developers, sysadmins, and open-source enthusiasts who want faster, more reliable scripts without wading through endless syntax. 【Book Arc】 - **Opening (~0%–13%)**: Frames Bash as a complete programming language and sets expectations for the third edition—Bash 5.2 coverage, rewritten idiomatic scripts, and a focus on avoiding common failure modes. - **Early (~13%–27%)**: Gets you writing immediately with the first shell program, covering script files, naming, directory placement, editors, and a basic "Hello, World!" workflow. - **Early (~27%–33%)**: Moves into input, output, and throughput: positional and special parameters, variables, arguments vs. options, and why `echo` should be avoided. - **Middle (~33%–60%)**: Continues the I/O theme with `printf` formatting, escape sequences, format specifiers, width control, printing to variables, and line continuation. - **Late (~60%–87%)**: Covers standard streams and redirection (`>`, `>>`, `<`), reading input, pipelines, and command substitution—the core of composing shell programs. - **Ending (~87%–100%)**: Introduces looping and branching: exit status, expression testing with `test`, `[ … ]`, file/integer/string tests, and the enhanced `[[ … ]]` construct. 【Key Takeaways】 - **Bash is a programming language, not just glue** (Opening): The book's central premise is that shell internals let Bash programs approach the speed of compiled utilities. This reframes how you approach scripting. - **Idiomatic Bash beats portable-but-clunky Bash** (Opening): The third edition rewrites scripts to exploit Bash-specific features rather than writing lowest-common-denominator shell code. - **Parameter expansion can replace external commands** (Early): Using shell expansion instead of spawning processes is a major performance lever and a recurring theme. - **Avoid `echo`; prefer `printf`** (Early–Middle): The excerpts explicitly flag `echo` as something to avoid, with `printf` offering reliable formatting, escape sequences, and width control. - **Special parameters are the plumbing of scripts** (Early): `*`, `@`, `#`, `0`, `$`, `?`, `_`, `!`, `-` govern arguments, status, and process context—essential for correct scripts. - **Redirection and pipelines are composition primitives** (Late): `>`, `>>`, `<`, pipelines, and command substitution are how small programs become larger tools. - **Exit status drives control flow** (Ending): Testing expressions and branching on exit status is the foundation of looping and decision-making in Bash. - **Test syntax matters** (Ending): The distinction between `test`/`[ … ]` and the enhanced `[[ … ]]` affects correctness and readability. 【Reading Tips】 - **Deep-read the early I/O chapters**: Parameters, `printf`, and redirection are the vocabulary you'll use in every later script; skimming here costs you later. - **Skim the setup material**: Script naming, directory selection, and editor choice are one-time concerns—read once, then move on. - **Practice the test constructs**: The `[ … ]` vs. `[[ … ]]` distinction is a common source of bugs; type out examples rather than just reading them. - **Keep the book's premise in mind**: Whenever you reach for an external command, ask whether parameter expansion or a builtin could do it faster. - **Use the exercises**: The excerpts show commands, concepts, and exercises at chapter ends—these are the fastest way to convert reading into skill. 【Coverage Limits】 The excerpts cover the front matter, table of contents, and early chapters through looping and branching; later chapters on web-facing scripts, readline/history usage, and advanced topics are referenced in the blurb but not detailed in the excerpts. Specific chapter titles beyond Chapters 1–3 are not covered.