Bash vs zsh Differences

Array starting indices differ. bash uses 0-based indexing; zsh uses 1-based indexing.

bash

users=("user1" "user2" "user3")
echo ${users[0]}
user1
echo ${users[1]}
user2

zsh

users=("user1" "user2" "user3")
echo ${users[1]}
user1
echo ${users[2]}
user2

In bash, an unquoted variable is automatically split on spaces. In zsh, it is not split.

bash

msg="hello world"
for word in $msg; do echo "[$word]"; done
[hello]
[world]

zsh

msg="user1"
for word in $msg; do echo "[$word]"; done
[user1]

Use the recursive glob (**) to search files in subdirectories. In bash, you must first run shopt -s globstar.

bash

shopt -s globstar
ls **/*.txt

zsh

ls **/*.txt

The behavior when a glob matches no files differs. bash passes the pattern string as-is, while zsh raises an error.

bash

ls *.xyz
ls: *.xyz: No such file or directory

zsh

ls *.xyz
zsh: no matches found: *.xyz

Prompt configuration syntax differs.

bash (~/.bashrc)

PS1='\u@\h:\w\$ '

zsh (~/.zshrc)

PS1='%n@%m:%~%# '

Shell option syntax differs.

bash

shopt -s nocaseglob
shopt -s globstar
shopt -u nocaseglob

zsh

setopt no_case_glob
setopt glob_star_short
unsetopt no_case_glob

Common Mistake 1: Array index difference causes wrong element to be retrieved

bash arrays are 0-based; zsh arrays are 1-based. The same code produces different results in each shell.

colors=("red" "green" "blue")
echo "${colors[0]}"
（bash: red /  zsh: empty string）

When writing scripts, specify #!/bin/bash to ensure consistent 0-based indexing.

Common Mistake 2: Glob with no matches behaves differently

When a glob pattern matches nothing, bash leaves it as a literal string by default, while zsh reports an error.

echo *.xyz
（bash: *.xyz /  zsh: zsh: no matches found: *.xyz）

Use nullglob in bash to suppress the unmatched glob.

shopt -s nullglob; echo *.xyz

A shell script written with #!/bin/bash always runs under bash syntax, so using zsh as your daily shell does not affect script behavior. The differences matter when you type commands directly in the terminal or when writing settings in ~/.bashrc vs ~/.zshrc.

The most important difference to watch for is the array starting index. bash is 0-based and zsh is 1-based, so the same code can produce different results. If portability matters, specify #!/bin/bash explicitly and run the script with bash.

For shebang usage, see shebang / chmod +x. For variable expansion, see ${Parameter Expansion}. For glob usage in for loops, see for.