tech-studies

Shell / Bash

3 min read

Shell / Bash

roadmap.sh: https://roadmap.sh/shell-bash

Suggested path through the Shell / Bash nodes. Each node links to its lesson when written.

Nodes

Shell fundamentals

  • What is a shell?
  • Shell vs terminal vs console
  • Bash vs sh vs zsh vs fish
  • Interactive vs non-interactive shells
  • Login vs non-login shells
  • The shebang line (#!/bin/bash)
  • Running a script (chmod +x, ./script, bash script)
  • Shell startup files (.bashrc, .bash_profile, .profile)

Basic commands

  • echo and printf
  • cd, pwd, ls
  • cp, mv, rm, mkdir, touch
  • cat, less, head, tail
  • man and help
  • history and command recall
  • alias and unalias
  • type, which, command

Variables and expansion

  • Defining and using variables
  • Quoting (single, double, backslash)
  • Command substitution $(…)
  • Arithmetic expansion $((…))
  • Parameter expansion and defaults
  • Special variables (?, $$, !, #, *)
  • Environment vs shell variables (export)
  • Brace expansion and tilde expansion

Input and output

  • Standard input, output, and error
  • Redirection (>, >>, <, 2>, &>)
  • Pipes (|)
  • Here documents and here strings
  • tee
  • /dev/null and /dev/stdin
  • read for user input

Control flow

  • if / elif / else
  • [[ ]] test command
  • case statements
  • for loops
  • while and until loops
  • break and continue
  • Exit codes and return
  • Logical operators (&&, ||, !)

Functions and scripts

  • Defining functions
  • Function arguments and return values
  • Local vs global variables
  • Positional parameters and shift
  • Parsing options (getopts)
  • Sourcing scripts
  • set options (set -e, -u, -x, -o pipefail)
  • Trap and signal handling

Text processing

  • grep and regular expressions
  • sed
  • awk
  • cut, paste, sort, uniq
  • tr, wc, fold
  • xargs
  • find with -exec
  • Globbing and wildcards

Arrays and data

  • Indexed arrays
  • Associative arrays
  • Iterating over arrays
  • String manipulation (substrings, replace, length)
  • Reading files line by line
  • IFS (Internal Field Separator)

Job control and processes

  • Foreground and background (&)
  • jobs, fg, bg
  • kill and signals
  • nohup and disown
  • Subshells and command grouping
  • wait and process synchronization
  • Command exit status and pipelines

Best practices and debugging

  • Quoting and word-splitting pitfalls
  • ShellCheck for static analysis
  • Debugging with set -x and bash -x
  • Writing portable POSIX scripts
  • Error handling patterns
  • Idempotency and safety
  • Style guides and readability

Resources

See resources.md.

Project ideas

  • Write a robust backup script with set -euo pipefail, option parsing via getopts, logging, and a trap that cleans up temp files on exit.
  • Build a CLI tool that parses a CSV with awk/cut and prints a formatted summary report, handling missing fields and edge cases.
  • Create a dotfiles bootstrap script that detects the OS, symlinks config files, and installs packages idempotently so it is safe to re-run.

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