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Bash: The Custom Grimoire

.bashrc — the file your shell reads every morning. Alias your typos, install your favourite functions permanently, and build a prompt that answers questions before you ask them.

Sep 29, 2026 · 4 min0% readbash bashrc dotfiles Wizardry of Bash · 13

Every shell you open runs a ritual first: it reads a file in your home directory called .bashrc and casts everything inside it. Every alias you've ever envied on a colleague's screen, every coloured prompt, every custom command — it all lives in this one plain-text spellbook. Today you write in it.

The grimoire on the shelf — fig. 13 — the custom grimoire: a well-worn .bashrc, annotated by its owner, kept within reach at all times

Meeting your grimoire

bash

cat ~/.bashrc        # read it (on macOS, you may need ~/.bash_profile or ~/.zprofile — see below)

You'll find lines like alias ll='ls -la' — souvenirs from whoever configured the machine. Boring to read, transformative to write. The golden rule:

Any spell you've typed more than three times, and typed with typos, is begging to become an alias. (Alias #1 for most wizards: alias gti='git'. You have a typo. You know the one.)

Aliases go in .bashrc, one per line:

bash

# ~/.bashrc — the grimoire
alias ll='ls -lahF'           # the good listing — details, human sizes, type symbols
alias la='ls -A'              # even hidden files, compact
alias ..='cd ..'              # the lazy climb
alias ...='cd ../..'          # the lazier climb
alias grep='grep --color=auto'   # matches in colour. No downside. Where has this been all my life.

Reload (that's source, from part 09, doing its job):

bash

source ~/.bashrc

From now on, every new shell you ever open is your shell: your shortcuts, your words.

The prompt: ask, and it shall answer

That nirmit@tower:~$ you've been reading since part 01? Configurable. The variable PS1 holds the recipe:

bash

echo "$PS1"    # the current recipe, in cryptic backslash-runes

The runes (a sample; the man page section "PROMPTING" has the full litany):

Rune	Shows
`\u`	your username
`\h`	the machine's short name
`\w`	current directory (full path; `\W` for just the name)
`\$`	`$` (or `#` if you're admin — the brake-less mode from part 01)
`\t`	24-hour time
`\e[0;32m` … `\e[0m`	start colour (green here) … stop colour

Compose your own — username in green, folder in purple, and a marker that screams when you're admin:

bash

PS1='\e[0;32m\u\e[0m:\e[0;35m\w\e[0m\$ '

Two lines of config, and your prompt now answers "who am I, where am I, whose privileges am I casting with" — every moment, for free, before you ask. The status questions of terminal life, automated. Put it in .bashrc and it's permanent.

The one-line prompt trick that saves ten questions a day

For git users — one status rune instead of typing git status compulsively:

bash

parse_git_branch() {
  git branch 2>/dev/null | sed -n 's/^\* \(.*\)/(\1)/p'
}
PS1='\e[0;35m\w\e[0m \e[0;36m$(parse_git_branch)\e[0m\$ '

Now the prompt itself reads ~/projects/spellbook (main)$ — branch visible before every cast. Part 10's sed finds the * main line in git branch output; command substitution from part 06 runs it every prompt. Three techniques from three parts, converged in two lines of config. This course has been building to a prompt, and it was worth it.

Functions in the grimoire

Aliases are for one-liners. For anything with logic, graduate to functions — written in .bashrc exactly as part 09 taught, but now permanent:

bash

# make a folder AND enter it. (A task so common bash never added it. We're not bitter.)
mcd() { mkdir -p "$1" && cd "$1"; }

# extract anything — the universal unpacker
extract() {
  case "$1" in
    *.tar.gz|*.tgz) tar -xzf "$1" ;;
    *.tar.bz2)      tar -xjf "$1" ;;
    *.zip)          unzip "$1" ;;
    *)              echo "Unknown archive: $1" ;;
  esac
}

# what's eating this folder?
fatty() { du -h "$1" 2>/dev/null | sort -rh | head -n 10; }

mcd, extract, fatty — three functions, permanently installed, ready in every shell you'll ever open. Part 09's factory, now bolted to the wall. And when a script needs testing interactively, source it — the workshop door swings both ways.

Keep the grimoire in git: dotfiles

One warning, one ritual:

The warning: .bashrc grows. People end up with 900-line files containing three conflicting PS1 definitions and a function nobody remembers writing. Comment your additions. Future-you is a different wizard with no memory of present-you's cleverness.
The ritual: keep it in a git repo named dotfiles, symlinked into place on every new machine:

bash

cd ~
git init dotfiles && cd dotfiles
cp ~/.bashrc .
git add .bashrc && git commit -m "the grimoire, v1"
ln -s ~/dotfiles/.bashrc ~/.bashrc    # the symlink: one file, many thrones

New machine? Clone the repo, run the ln -s, source it — your entire shell environment, installed in a minute. This is what people mean by "dotfiles on GitHub", and it's the single highest-leverage hour you'll spend on your terminal setup.

Your quest

Add three aliases for things you actually type badly or often
Install the git-branch prompt; commit something; watch (main) appear
Write mcd and extract into .bashrc, source it, use them from a fresh terminal — permanence is the point
Start the dotfiles repo. One file. Future machines will thank you.

Next: part 14 — The Wider Realm, where bash leaves your machine: ssh, cron, git hooks, and CI — the places shell skills compound into power.

Filed under Wizardy of Bash — part 13 of 15 · Previous: Jobs & Signals · Next: The Wider Realm

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