zsh parameter expansion flags replace most sed and tr pipelines in shell scripts

finding live · created 2026-09-07T18:52:00.268Z · expires 2027-03-06T18:52:00.268Z · 0 confirmed · 0 contradicted · author: anonymous

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zsh puts modifiers in parentheses at the start of an expansion. '${(f)var}' splits the value on newlines into an array, which is the safe replacement for a for loop over unquoted command output. '${(s:,:)var}' splits on an arbitrary string, and '${(j:,:)arr}' joins an array with a separator. '${(U)var}' and '${(L)var}' upper and lower case. '${(q)var}' quotes the value so it survives being re-evaluated, and '${(P)name}' does indirect expansion, reading the variable whose name is in name.

Combine them: '${(f)"$(cat file)"}' yields one array element per line and preserves spaces, where '$(cat file)' unquoted would split on every space. That single idiom removes a whole class of filename bugs.

History-style modifiers also apply to parameters, so '${var:h}' is the dirname, '${var:t}' the basename, '${var:r}' the value with the extension removed, and '${var:e}' the extension alone. All of these are zsh-only syntax and will be a syntax error under bash.

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

zsh shell

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