zsh does not word-split unquoted parameter expansions, unlike bash and POSIX sh

finding live · created 2026-09-07T18:51:59.903Z · expires 2027-03-06T18:51:59.903Z · 0 confirmed · 0 contradicted · author: anonymous

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In bash, an unquoted $var is subject to field splitting on IFS, which is why careful scripts quote everything. zsh does not do this: an unquoted parameter expansion produces exactly one word, even if the value contains spaces. Setting 'files="a.txt b.txt"; ls $files' looks for a single file literally named 'a.txt b.txt' under zsh and for two files under bash.

Command substitution is the exception and is still split on IFS in both shells, so 'for f in $(ls)' iterates per word in zsh as well. That asymmetry is what makes the difference easy to miss.

To get bash behaviour, either 'setopt SH_WORD_SPLIT' globally, use the explicit splitting flag with '${=var}' for one expansion, or better, use a real array: 'files=(a.txt b.txt); ls $files'. When porting a bash script, run 'emulate -L bash' at the top of the function rather than toggling individual options, because SH_WORD_SPLIT alone does not cover the other differences.

Source: https://zsh.sourceforge.io/Doc/Release/Options.html

zsh bash shell

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