Explain .zshrc code

What this .zshrc sample shows

when it runs

zsh reads ~/.zshrc each time it starts an interactive shell, a terminal you type into, and that includes a login shell: zsh -l -i had the ll alias too. A script run with zsh -c doesn't read it: there whence -v ll said ll not found. bash ignores the file completely.

history and options

HISTSIZE is how many commands a session keeps in memory and SAVEHIST how many the history file keeps. With SHARE_HISTORY on, each command is written to HISTFILE as you type it, so every open terminal sees the others' commands, and HIST_IGNORE_DUPS skips a command typed twice in a row. setopt listed both as sharehistory and histignoredups.

path and typeset -U

In zsh, the array path and the text PATH are the same list, so path=(~/bin $path) puts ~/bin first, and command -v hello found the hello script there. typeset -U path keeps each folder once: after adding ~/bin again and re-reading the file, it was still listed 1 time. Without that line, two re-reads left it listed 3 times.

aliases, functions and the prompt

whence -v ll printed ll is an alias for ls -lah, and mkcd a/b made both folders and moved into them. In PROMPT, %F{blue} and %f start and stop the color, %~ is the folder with your home shown as ~ and %# is % for you or # for root: in ~/proj the prompt read ~/proj % with the folder in blue.

Good to know

• Run with zsh 5.9.2 on a test home folder, so nothing touched a real ~/.zshrc. compinit wrote its cache, a .zcompdump file, into that folder on the first run.
• zsh doesn't split a variable on spaces the way bash does: with f="my file.txt", set -- $f gave 1 argument in zsh and 2 in bash. Code copied from a bash script can behave differently here.
• zsh arrays start at 1, not 0: with a=(x y z), ${a[1]} was x.

Watch out: Settings that scripts need don't belong in .zshrc. A script run as zsh -c saw none of it: ll not found, ~/bin wasn't on its path and command -v hello found nothing. A variable exported in ~/.zshenv, which zsh reads for every shell, reached the same script: it printed SHOP_ENV=[dev].