Which startup file runs¶

Level: 101 · you put a line in ~/.bashrc, opened a new terminal, and nothing changed

One line: A shell picks its startup files by two questions, whether it is a login shell and whether it is interactive, and each shell answers them with different files. bash reads ~/.bash_profile for a login shell and ~/.bashrc for an interactive one, and a shell that is both reads only ~/.bash_profile. zsh reads ~/.zshenv every time and adds ~/.zprofile and ~/.zshrc as they apply. fish reads config.fish every time and lets the file ask.

Measured¶

Seven files under a throwaway HOME each print their own name: ~/.bashrc, ~/.bash_profile, ~/.profile, ~/.zshenv, ~/.zprofile, ~/.zshrc and ~/.config/fish/config.fish. Each shell is then started four ways, always with -c true, a command that prints nothing, so every line that appears came from a startup file:

-c true alone is the kind of shell a script runs in.
-l makes it a login shell, the kind a Mac's Terminal opens (see On a Mac).
-i makes it interactive, a shell that expects a person to type.
-l -i is both.

stdin is /dev/null, and each shell's stderr is thrown away: an interactive bash with no terminal says it has no job control, and on Linux it also names a process-group number that changes between runs.

Verified output of startup_files_sh.sh, identical on Linux and macOS — regenerated by tools/run_examples.py, never hand-typed.

$ cat ~/.bashrc
echo '  ~/.bashrc'

$ bash -c true
  (none)

$ bash -l -c true
  ~/.bash_profile

$ bash -i -c true
  ~/.bashrc

$ bash -l -i -c true
  ~/.bash_profile

$ rm ~/.bash_profile

$ bash -l -i -c true
  ~/.profile

$ cat ~/.bash_profile
echo '  ~/.bash_profile'
[ -r ~/.bashrc ] && . ~/.bashrc

$ bash -l -i -c true
  ~/.bash_profile
  ~/.bashrc

$ bash --norc -i -c true
  (none)

$ bash --noprofile -l -c true
  (none)

A script reads none of them. bash -c true printed (none).
bash answers each question with one file. The login shell read ~/.bash_profile, the interactive shell read ~/.bashrc, and the shell that is both read only ~/.bash_profile. A line that is only in ~/.bashrc never reaches a login shell.
~/.profile is a fallback. After rm ~/.bash_profile, the same login shell read ~/.profile instead. The bash manual ↗ gives the order: ~/.bash_profile, ~/.bash_login, ~/.profile, and the first one that exists.
The usual fix is one line. A ~/.bash_profile that sources ~/.bashrc made the login shell read both.
--norc and --noprofile switch the two off. The prompt page runs bash with --norc to keep a ~/.bashrc out.

On a Mac¶

The files in your home folder behave the same way. The three keys on this page are shared: macOS's bash 3.2 read exactly the files that Ubuntu's bash 5.2 read, and so did the two zsh builds and the two fish builds.

The files in /etc run first, and they do differ. With a HOME that holds nothing but an empty ~/.zshrc (so zsh does not offer to write one), the prompt each shell starts with is whatever a system file set, or else the shell's own default:

Verified output of startup_system_prompt_sh.sh on Linux — regenerated by tools/run_examples.py, never hand-typed.

$ bash -i -c 'echo "$PS1"'
${debian_chroot:+($debian_chroot)}\u@\h:\w\$ 

$ bash -l -i -c 'echo "$PS1"'
${debian_chroot:+($debian_chroot)}\u@\h:\w\$ 

$ zsh -i -c 'print -r -- "$PS1"'
%m%# 

$ zsh -f -i -c 'print -r -- "$PS1"'
%m%#

Verified output of startup_system_prompt_sh.sh on macOS — regenerated by tools/run_examples.py, never hand-typed.

$ bash -i -c 'echo "$PS1"'
\s-\v\$ 

$ bash -l -i -c 'echo "$PS1"'
\h:\W \u\$ 

$ zsh -i -c 'print -r -- "$PS1"'
%n@%m %1~ %# 

$ zsh -f -i -c 'print -r -- "$PS1"'
%m%#

bash on macOS sets no prompt for a shell that is not a login shell, so it keeps bash's built-in default, \s-\v\$. A login bash gets \h:\W \u\$, the prompt macOS's /etc/bashrc sets. bash on Ubuntu gets \u@\h:\w\$, behind a debian_chroot test, the prompt Ubuntu's /etc/bash.bashrc sets, whether it is a login shell or not.
zsh on macOS gets %n@%m %1~ %#, the prompt macOS's /etc/zshrc sets. zsh on Ubuntu has no system prompt, so zsh -i starts with zsh's own %m%#, the same prompt as zsh -f, which reads no files at all.
They do more than set a prompt. Read, not run here: macOS's /etc/zprofile rebuilds PATH with path_helper, and Ubuntu's /etc/bash.bashrc prints a hint about sudo to members of the sudo group unless ~/.hushlogin exists, which is why the bash scripts on these two pages create one. The rest of this library's examples run zsh with -f and fish with --no-config, so that no system file can change their output.

Terminal.app opens a login shell; a Linux desktop terminal usually does not. Neither is measured by CI, which has no terminal windows, so both are documented behaviour:

On a Mac, a new Terminal window runs your shell as a login shell: About bash_profile and bashrc on macOS ↗ explains that Terminal runs .bash_profile where other systems run .bashrc. On the Mac this page was written on (macOS 26.6, checked with ps on 2026-09-13), Terminal's child process was login -pf with the user's name, and its child was -fish. A shell whose name starts with - is a login shell (bash manual, Invoking Bash ↗).
On Linux, a terminal emulator starts a plain shell, not a login shell, unless it is told to: Greg's Wiki, DotFiles ↗ walks through xterm starting /bin/bash without the -, and its -ls flag for a login shell. GNOME Terminal keeps the choice as a profile setting, Run command as a login shell (GNOME Terminal help ↗).

So a line in ~/.bashrc, the file a Linux book names, is read by a Linux terminal window and skipped by a Mac's. In bash on a Mac, put the line in ~/.bash_profile, or give ~/.bash_profile the one-line fix above. And unless you changed it, the shell in a Mac's Terminal is zsh, not bash.

In zsh and fish¶

zsh has three files where bash has two, and they add up instead of standing in for each other:

Verified output of startup_files_zsh.zsh, identical on Linux and macOS — regenerated by tools/run_examples.py, never hand-typed.

$ cat ~/.zshrc
echo '  ~/.zshrc'

$ zsh -c true
  ~/.zshenv

$ zsh -l -c true
  ~/.zshenv
  ~/.zprofile

$ zsh -i -c true
  ~/.zshenv
  ~/.zshrc

$ zsh -l -i -c true
  ~/.zshenv
  ~/.zprofile
  ~/.zshrc

$ zsh -f -l -i -c true
  (none)

~/.zshenv runs every time, zsh -c included, and that is the kind of zsh a script runs in. A line that prints something, or takes a while, belongs in one of the other two.
~/.zprofile is for a login shell and ~/.zshrc for an interactive one, and a shell that is both reads both. A Mac's Terminal opens a login shell that is also interactive, so it reads ~/.zshrc: in zsh, the book's advice works with the file name changed.
zsh read neither ~/.profile nor ~/.bashrc in any of the four runs.
-f reads nothing. It is how this library runs every zsh example.

fish reads one file every time, and the file asks what kind of shell is reading it:

Verified output of startup_files_fish.fish, identical on Linux and macOS — regenerated by tools/run_examples.py, never hand-typed.

$ cat ~/.config/fish/config.fish
echo '  ~/.config/fish/config.fish'
status is-login; and echo '    status is-login'
status is-interactive; and echo '    status is-interactive'

$ fish -c true
  ~/.config/fish/config.fish

$ fish -l -c true
  ~/.config/fish/config.fish
    status is-login

$ fish -i -c true
  ~/.config/fish/config.fish
    status is-interactive

$ fish -l -i -c true
  ~/.config/fish/config.fish
    status is-login
    status is-interactive

$ fish -c true
  ~/.config/fish/conf.d/prompt.fish
  ~/.config/fish/config.fish

$ fish --no-config -l -i -c true
  (none)

config.fish ran all four times, fish -c included. status is-login and status is-interactive are how it tells the four apart, so a line meant only for a person at a prompt goes inside if status is-interactive … end.
Files in ~/.config/fish/conf.d/ run too, before config.fish.
fish read none of bash's or zsh's files.
--no-config reads nothing. It is how this library runs every fish example.
A prompt does not go in any of these. funcsave fish_prompt writes it to ~/.config/fish/functions/, and fish loads it from there by itself: see PS1 belongs to bash.

The four runs, side by side:

	bash	zsh	fish
a script, `-c`	nothing	`~/.zshenv`	`config.fish`
login, `-l`	`~/.bash_profile`, else `~/.profile`	`~/.zshenv`, `~/.zprofile`	`config.fish`; `status is-login` succeeds
interactive, `-i`	`~/.bashrc`	`~/.zshenv`, `~/.zshrc`	`config.fish`; `status is-interactive` succeeds
both, `-l -i`	`~/.bash_profile` only	all three	`config.fish`; both succeed
read nothing	`--norc`, `--noprofile`	`-f`	`--no-config`

If you are coming from another library¶

Rust. Fuzzy finding ↗ sets up fzf's key bindings with one line in config.fish, ~/.bashrc or ~/.zshrc. In bash on a Mac, the ~/.bashrc line needs the ~/.bash_profile fix above before a Terminal window sees it.
Encodings. Locale and LC_CTYPE ↗ covers Terminal's Set locale environment variables on startup, which puts LANG into the environment of the shell Terminal starts, before any of these files run.

Which startup file runs¶

Measured¶

On a Mac¶

In zsh and fish¶

If you are coming from another library¶

See also¶