Shell scripting

Topics

1. 01

   Shell scripting basics

   What a script is, the shebang line, making a script executable, and running it.

   7 min
2. 02

   Shell variables

   Setting and reading variables, quoting, command substitution, and environment variables in scripts.

   9 min
3. 03

   Conditionals

   if, test and [[ ]], comparing strings, numbers and files, and case statements.

   11 min
4. 04

   Loops

   for, while and until loops, reading a file line by line, and break and continue.

   11 min
5. 05

   Parameter expansion

   Default values, trimming and replacing parts of a value, and lengths, without calling other programs.

   9 min
6. 06

   Arguments and input

   Positional arguments, shift, options with getopts, reading input, and a usage message.

   12 min
7. 07

   Functions

   Defining functions, arguments and return values, local variables, and splitting a script into parts.

   10 min
8. 08

   Arrays

   Indexed and associative arrays, looping over them, and keeping file names with spaces intact.

   11 min
9. 09

   Arithmetic and strings

   Integer maths with $(( )), comparing and formatting numbers and text, and printf.

   12 min
10. 10

    Exit codes and errors

    Exit statuses, checking them, && and ||, writing errors to stderr, and exiting with the right code.

    11 min
11. 11

    Robust scripts

    set -euo pipefail, traps and clean-up, temporary files, lock files, and scripts that are safe to run twice.

    12 min
12. 12

    Debugging

    Tracing a script with set -x, ShellCheck, and finding the line where it goes wrong.

    13 min
13. 13

    Real-world scripts

    Patterns from scripts that run in production: logging, configuration files, dry runs, and running from cron.

    15 min