Zsh vs Fish

Both ditched bash defaults — zsh stayed POSIX-ish, fish broke the syntax to make it friendlier.

Summary

Zsh is bash's power-user cousin — adds smarter globbing, better tab-completion, plugin frameworks like Oh My Zsh, but remains close enough to bash that most scripts run unchanged. Default macOS shell since Catalina.

Fish is a fresh design — interactive niceties (autosuggestions, syntax highlighting, sane defaults) at the cost of POSIX compatibility. Scripts that work in bash/zsh will often **fail to parse** in fish.

Practical rule: zsh is what you use when you want bash with fewer rough edges. Fish is what you use when you treat the shell as primarily an interactive tool, not a scripting engine.

Syntax & semantic differences

POSIX compatibility
Zsh
Mostly POSIX-compatible — most bash scripts run unchanged. Quirks: word-splitting is disabled by default (`$var` does not split).
Fish
Deliberately non-POSIX. Most bash scripts fail to parse in fish — fish is its own language.
Variable assignment
Zsh
`name=value` (POSIX) or `typeset name=value`. No `set` needed.
Fish
`set name value` — the verb-form is the only way. `name=value` works in `env`-style command prefixes only.
Fish `set` is the assignment command, not a shell option. `set -x name value` is **export**, not "trace mode" as in bash.
Reading variables
Zsh
`$name` or `${name}` — same as bash.
Fish
`$name` works; `${name}` does **not** — fish has no brace expansion of variables.
Arrays
Zsh
Native arrays. 1-indexed (different from bash's 0-indexed!). `arr=(a b c); echo $arr[1]` prints `a`.
Fish
Every variable is implicitly a list. 1-indexed. `set arr a b c; echo $arr[1]` prints `a`.
Conditional
Zsh
`if [[ -f file ]]; then ...; fi` — `[[ ]]` is built-in.
Fish
`if test -f file; ...; end` — no `[[ ]]`, use `test` (also aliased as `[ ... ]`) and `end` instead of `fi`.
Loops
Zsh
`for f in *.log; do ...; done`
Fish
`for f in *.log; ...; end` — terminator is `end`, not `done`.
Functions
Zsh
`my_fn() { echo $1 }` — args are `$1`, `$2`, `$@`.
Fish
`function my_fn; echo $argv[1]; end` — args are in `$argv`. Functions are auto-saved to `~/.config/fish/functions/`.
Command substitution
Zsh
`$(cmd)` (preferred) or backticks (legacy).
Fish
`(cmd)` — bare parentheses. `$(cmd)` is **not** supported; backticks are not supported.
Aliases / shortcuts
Zsh
`alias name='cmd'` — like bash. Sticks in interactive shells.
Fish
`alias name='cmd'` exists but is just a function wrapper. The idiomatic shortcut is `abbr name expansion` — expands at the prompt so you see the real command before running.
String math
Zsh
`$((1 + 2))` arithmetic expansion is built-in.
Fish
No `$((...))`. Use `math 1 + 2` or `math "1 + 2"`.
"Set and forget" PATH
Zsh
`export PATH="$HOME/bin:$PATH"` in `~/.zshrc`.
Fish
`fish_add_path $HOME/bin` — universal-variable helper. Or `set -Ux PATH $HOME/bin $PATH` once (`-U` = universal, persists across sessions).
Fish's universal variables are stored in `~/.config/fish/fish_variables`, not in any shell rc — easy to confuse if you're used to editing rc files.
Configuration file
Zsh
`~/.zshrc` (interactive), `~/.zprofile` (login), `~/.zshenv` (every invocation).
Fish
`~/.config/fish/config.fish`. Per-function and per-completion files live in `~/.config/fish/functions/` and `~/.config/fish/completions/`.
Glob qualifiers
Zsh
Zsh has glob qualifiers — `ls *(.m-1)` lists files modified in last day, `*(/)` lists only dirs. Powerful, terse.
Fish
No qualifiers — use `find` or filter with `string match` / `path filter`.

Side-by-side commands

The 32 most-compared commands in Zsh and Fish. See all Zsh commands · See all Fish commands.

aliasCreate a shortcut name for a longer command line.
Zsh
```
alias ll='ls -la'
```
Fish
```
alias ll='ls -la'
```
awkPattern scanning and processing language for structured text.
Zsh
```
awk '{print $1}' file
```
Fish
```
awk '{print $1}' file
```
catPrint file contents to standard output.
Zsh
```
cat file.txt
```
Fish
```
cat file.txt
```
chmodChange file mode bits (read / write / execute permissions) on Unix files.
Zsh
```
chmod 755 file
```
Fish
```
chmod 755 file
```
cpCopy files and directories.
Zsh
```
cp source dest
```
Fish
```
cp source dest
```
curlTransfer data from or to a server over HTTP, HTTPS, FTP, and many other protocols.
Zsh
```
curl https://example.com
```
Fish
```
curl https://example.com
```
cutExtract sections (fields or characters) from each line.
Zsh
```
cut -d',' -f1 file.csv
```
Fish
```
cut -d',' -f1 file.csv
```
echoPrint arguments to standard output, separated by spaces, followed by a newline.
Zsh
```
echo "hello world"
```
Fish
```
echo "hello world"
```
exportSet an environment variable and mark it for export to child processes.
Zsh
```
export NAME=value
```
Fish
```
set -gx NAME value
```
findLocate files by name, size, time, or other attributes.
Zsh
```
find . -name "*.log"
```
Fish
```
find . -name "*.log"
```
grepSearch file contents for a pattern.
Zsh
```
grep -r "pattern" .
```
Fish
```
grep -r "pattern" .
```
headOutput the first lines of a file.
Zsh
```
head -n 10 file
```
Fish
```
head -n 10 file
```
historyShow previously run commands from the shell history.
Zsh
```
history
```
Fish
```
history
```
killSend a signal to a process (typically to terminate it).
Zsh
```
kill <pid>
```
Fish
```
kill <pid>
```
lsList directory contents.
Zsh
```
ls -la
```
Fish
```
ls -la
```
mkdirCreate a new directory.
Zsh
```
mkdir dir
```
Fish
```
mkdir dir
```
mvMove or rename files and directories.
Zsh
```
mv source dest
```
Fish
```
mv source dest
```
pingSend ICMP echo requests to test reachability and round-trip latency.
Zsh
```
ping example.com
```
Fish
```
ping example.com
```
psList a snapshot of currently running processes.
Zsh
```
ps aux
```
Fish
```
ps aux
```
rmDelete files and directories.
Zsh
```
rm file
```
Fish
```
rm file
```
sedStream editor for filtering and transforming text.
Zsh
```
sed 's/old/new/g' file
```
Fish
```
sed 's/old/new/g' file
```
sortSort lines of text.
Zsh
```
sort file
```
Fish
```
sort file
```
sshOpen a secure shell on a remote host or run a remote command.
Zsh
```
ssh user@host
```
Fish
```
ssh user@host
```
tailOutput the last lines of a file.
Zsh
```
tail -n 10 file
```
Fish
```
tail -n 10 file
```
tarBundle and unbundle files into a single archive (often combined with gzip / bzip2 / xz).
Zsh
```
tar -czf archive.tar.gz dir/
```
Fish
```
tar -czf archive.tar.gz dir/
```
topInteractive process viewer — show running processes sorted by CPU or memory, refreshed in place.
Zsh
```
top
```
Fish
```
top
```
touchCreate an empty file or update its modification time if it exists.
Zsh
```
touch file.txt
```
Fish
```
touch file.txt
```
wcCount lines, words, or bytes.
Zsh
```
wc -l file
```
Fish
```
wc -l file
```
wgetNon-interactive network downloader for HTTP, HTTPS, and FTP.
Zsh
```
wget https://example.com/file.zip
```
Fish
```
wget https://example.com/file.zip
```
whichLocate an executable in PATH and print its full path.
Zsh
```
which python3
```
Fish
```
which python3
```
xargsBuild and execute command lines from standard input.
Zsh
```
find . -name '*.tmp' | xargs rm
```
Fish
```
find . -name '*.tmp' | xargs rm
```
zipPackage and compress files into a ZIP archive.
Zsh
```
zip -r archive.zip dir/
```
Fish
```
zip -r archive.zip dir/
```

Gotchas when porting between them

A bash script with `#!/usr/bin/env bash` runs fine on a fish system — fish only matters when **fish is the interpreter**. Don't panic about portability if your scripts have the right shebang.
Zsh word-splitting differs from bash: `$var` does **not** split on whitespace by default. Set `SH_WORD_SPLIT` or use `${=var}` to force splitting (bash behavior).
Fish has no `&&` / `||` — wait, it does, since fish 3.0. Older docs say to use `; and` / `; or`. Both work in fish 3.x+, but `; and` is still the documented idiom for scripts.
Zsh `setopt` options are different from bash `shopt` options. `setopt nullglob` (no-match → empty) vs bash `shopt -s nullglob`.
Fish does not honor `~/.bashrc` or `~/.profile`. Environment variables set by login scripts in bash terms may not be visible in a fish login.

Zsh vs Fish

Summary

Syntax & semantic differences

POSIX compatibility

Variable assignment

Reading variables

Arrays

Conditional

Loops

Functions

Command substitution

Aliases / shortcuts

String math

"Set and forget" PATH

Configuration file

Glob qualifiers

Side-by-side commands

Gotchas when porting between them

Full references

Other comparisons