Shell Programming

These materials are from a short course on shell (Bash) programming that I teach periodically. The course is organized into a number of topics, taught mostly sequentially. For each topic, there is a short text file providing a brief introduction, code examples, and sometimes, exercises and references. These files are not intended to replace a proper learning resource like a textbook. Instead, they serve as a resource for me to discuss topics and create scripts based on the fundamentals described within. Feel free to use them as you deem appropriate.

Contents

1. The shell
2. Simple commands
3. Compound commands: pipelines
4. Compound commands: lists
5. Execution environment
6. Redirections
7. Shell scripts
8. Hello world
9. echo
10. printf
11. Variables
12. Variables: declaration
13. Variables: types
14. Variables: scope and environment
15. Variables: builtins
16. Variables: read
17. Command substitution
18. Quoting and expansions
19. Patterns: globbing
20. Patterns: brace
21. String operations
22. Positional parameters
23. Integers and arithmetic expressions
24. Conditional statements
25. Conditional statements 2
26. Conditional statements 3
27. case
28. select
29. Arrays
30. for loops
31. while loops
32. until loops
33. break and continue
34. Functions
35. The fork bomb
36. Signals and traps
37. Debugging
38. xargs
39. getopts
40. eval
41. Obfuscation
42. Terminals
43. Shell configuration

Resources

• Official sources and references
  • BASH — The GNU Bourne-Again Shell
  • The GNU Bash Reference Manual
  • POSIX.1-2017 (see Shell & Utilities, Chapter 2)
  • Chet Ramey. Two papers on the design of Bash.
• Programming guides
  • Machtelt Garrels. Bash Guide for Beginners
  • Mendel Cooper. Advanced Bash-Scripting Guide
• Programming style and tools
  • Google Shell Style Guide
  • Bash pitfalls - A compilation of common mistakes made by Bash users
  • ShellCheck
• GNU coreutils
  • GNU Coreutils
  • Decoded: GNU coreutils
• The shell and the UNIX Philosophy
  • Askar Safin. The Collapse of the UNIX Philosophy
  • John D. Cook. Improving on the UNIX shell
  • James Hague. Don't Fall in Love With Your Technology
• Terminals
  • Linus Åkesson. The TTY demystified
  • Nicola Apicella. Linux terminals, tty, pty and shell
  • The Valuable Dev. A Guide to the Terminal, Console, and Shell.
• Script collections
  • Appendix A from the ABS Guide: Contributed Scripts
  • Ruan YiFeng. A collection of simple Bash scripts
  • Quine programs (including one in Bash)
  • For computer security folks:
    • A minimal TLS 1.2 implementation in a pure Bash script
    • SHA256 in (mostly) pure Bash script
    • Orc: A simple post-exploitation toolkit written in Bash
    • VShell, a clever shell command injection method.
    • Super Evil Shell Scripts
    • Beautified Bash malware
• Micellanea
  • J.A. Neitzel. V6 Sh History
  • Symbol pronunciation
  • The #! magic
  • A copy of the now defunct Bash Hackers wiki