Your team's shared .bashrc is being ported to .zshrc after everyone's login shell changed to zsh. Beyond word splitting and array indexing, which bash-specific constructs in that file will simply not work under zsh, and what replaces each?

## Start by separating what is portable Most of a typical `.bashrc` is not bash-specific at all. Exported variables, `alias` definitions, POSIX-shaped functions, `[[ ... ]]` conditionals, `$RANDOM`, `$SECONDS`, and `command -v` checks all behave the same in zsh. Those move across untouched. The work is in the bash-only remainder, and the honest way to do the migration is a line-by-line audit rather than a hopeful copy. ## The construct-by-construct list **`shopt` → `setopt` / `unsetopt`.** zsh has no `shopt` builtin at all; the line fails outright with a command-not-found. The option *names* also differ, so it is not a mechanical rename. `shopt -s histappend` has no single equivalent — zsh's history-appending behaviour is governed by `APPEND_HISTORY` (on by default) and `INC_APPEND_HISTORY`. `shopt -s checkwinsize` is unnecessary; zsh tracks terminal size itself. **History variables.** `HISTCONTROL=ignoreboth` and `HISTFILESIZE` are bash variables that zsh ignores silently — the worst kind of failure, because the file sources cleanly and your history behaves differently. In zsh, `HISTSIZE` is the in-memory size and **`SAVEHIST`** is how many lines are written to `HISTFILE`; if `SAVEHIST` is unset or zero, nothing is written at all, which is the classic "my zsh history disappears" report. The `ignoreboth` behaviour splits into two options: `HIST_IGNORE_DUPS` and `HIST_IGNORE_SPACE`. **`PROMPT_COMMAND` → `precmd`.** bash runs the contents of `PROMPT_COMMAND` before each prompt. zsh calls a function named `precmd`, and also every function whose name is in the `precmd_functions` array — the array is what you should append to, so you do not clobber another plugin's hook. The sibling hook `preexec` runs after you accept a line and before the command executes, which bash gained an equivalent for only much later. **Prompt strings.** zsh does not understand bash's backslash escapes such as `\u` and `\w`; it has its own percent-escape vocabulary, and command or parameter substitution inside a prompt requires enabling `PROMPT_SUBST`. Expect to rewrite the prompt rather than translate it. **Completion scripts.** A file that calls `complete -F _foo foo` or `compgen -W` is using bash builtins zsh does not natively provide. zsh can load a shim: ```zsh autoload -U +X bashcompinit && bashcompinit source /path/to/foo-completion.bash ``` That is a compatibility layer, not a translation — it works for many vendor-supplied completion files and can be flaky for elaborate ones. **`${BASH_SOURCE[0]}`.** Widely used in dotfiles to find the directory a sourced file lives in. It does not exist in zsh. In zsh, `$0` inside a sourced file is the file's path, so the idiom becomes `${0:A:h}` (zsh's `:A` modifier resolves to an absolute path, `:h` takes the directory). **`read -p prompt var`.** zsh's `read` does not take `-p` as a prompt flag; the prompt is attached to the variable name as `read "var?Prompt: "`. Similarly, bash's `read -a arr` is `read -A arr` in zsh. **PATH management.** zsh ties the scalar `PATH` to an array named `path` (and `FPATH` to `fpath`, `CDPATH` to `cdpath`). `typeset -U path` makes it deduplicate automatically, which replaces the hand-rolled "is this already in PATH" loop most `.bashrc` files carry. ## The strategy, not just the list For a team file, the durable answer is to stop maintaining one file per shell. Put everything portable — exported variables, aliases, POSIX functions — in a `~/.shell_common` sourced from both `.bashrc` and `.zshrc`, and keep only shell-specific lines in each rc. Two rules make that work: quote every expansion (so the file means the same thing under both splitting regimes), and use `"${arr[@]}"` for arrays. Guard genuinely shell-specific blocks by feature detection rather than by shell name where you can — `(( $+commands[foo] ))` in zsh versus `command -v foo` in both — and where you cannot, branch on `${ZSH_VERSION:-}` / `${BASH_VERSION:-}`, which are set only by their own shell. Finally, port incrementally and verify: source the new file in a fresh interactive shell and check the things that fail *silently* — history actually persisting to disk, PATH order, and the prompt hooks firing — because the loud failures like `shopt: command not found` will find you on their own.