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typeset — Declare a variable or set its attributes (zsh canonical name) across all 5 shells

Equivalents in every shell

Bashunix
typeset -i count=0

Bash accepts `typeset` as a SYNONYM for `declare` (POSIX-historical alias). Same flag set — `-i` integer, `-r` readonly, `-a` indexed array, `-A` associative, `-x` export, `-g` global-from-inside-function. New bash scripts conventionally use `declare`; `typeset` exists for ksh / zsh portability.

Zshunix
typeset -i count=0

Canonical name in zsh (bash's `declare` works too but is non-idiomatic). Zsh-specific flags include `-T scalar=array sep` (tie scalar to array via separator), `-U` (unique elements in array), and `-A` (associative array — different access syntax from bash via `${(@kv)hash}`).

Fishunix
set -l count 0

Fish has NO `typeset` or `declare`. `set` with scopes — `-l` (local), `-g` (global), `-U` (universal — persisted across sessions in `~/.config/fish/fish_variables`), `-x` (export) — covers all attribute combinations. Every variable is a LIST; no separate array primitive.

PowerShellwindows
[int]$count = 0

A type cast on the LHS gives a typed variable; subsequent assignments coerce or throw. `New-Variable -Name x -Value 1 -Option ReadOnly,AllScope` covers readonly + scope. Hashtables (`@{key=val}`) play the role of associative arrays.

cmd.exewindows
set /a count=0

`set /a` declares an integer (signed 32-bit) with arithmetic parsing of the RHS. Plain `set name=value` always creates a STRING. No arrays, no readonly, no associative variables — cmd's variable model is one flat string namespace.

Worked examples

Declare a typed integer variable

Bash
typeset -i count=0
Zsh
typeset -i count=0
Fish
set -l count 0
PowerShell
[int]$count = 0
cmd.exe
set /a count=0

Declare a readonly variable

Bash
typeset -r MAX=100
Zsh
typeset -r MAX=100
PowerShell
Set-Variable MAX 100 -Option ReadOnly

Declare an associative array / hashmap

Bash
typeset -A user; user[name]=alice
Zsh
typeset -A user; user[name]=alice
PowerShell
$user = @{ name = 'alice' }

Gotchas

  • `typeset` and `declare` are the SAME builtin in bash. `typeset` came first historically (ksh, zsh) and bash adopted it as an alias — pick ONE per project for grep-ability. Zsh scripts conventionally use `typeset`; bash scripts conventionally use `declare`. See the existing /cmd/declare page for the shared semantics.
  • Inside a function, `typeset X=v` makes `X` LOCAL to that function — even without `-l`. To declare a function-internal variable that is GLOBAL, use `typeset -g X=v`. Forgetting `-g` is a common cause of "why does this variable reset after the function returns?" bugs.
  • Zsh's `typeset -U` (unique array) silently DEDUPLICATES on every assignment — `arr=(a b a c)` becomes `(a b c)`. Bash has no equivalent; porting a zsh `typeset -U PATH` to bash needs explicit dedup logic (`awk '!seen[$0]++'`) to keep the same behaviour.
  • Bash `typeset -i x=5+3` evaluates the RHS as arithmetic — `$x` is `8`, not `5+3`. Subsequent assignments are ALSO arithmetic-parsed for the lifetime of `x`. Without `-i`, assignment is literal-string. The flag is sticky and reaches across function boundaries.
  • POSIX `/bin/sh` (dash, ash, busybox sh) does NOT implement `typeset` OR `declare`. Scripts with `#!/bin/sh` headed for Alpine, OpenWrt, or Debian `dash` MUST use plain `x=value` and `readonly x` — these are the only POSIX-portable primitives. `shellcheck` flags this with code SC2039.

WSL & PowerShell Core notes

pwshPowerShell `[int]`, `[string]`, `[datetime]` type casts behave identically on Windows, Linux, and macOS pwsh. The "stick a type to a variable for life" attribute that bash `typeset -i` provides has no direct pwsh equivalent — pwsh enforces type on each assignment via the cast on the LHS, not as a sticky attribute.
WSLInside WSL, `typeset` is bash / zsh exactly as on native Linux. Variables declared inside WSL do NOT propagate to Windows-side processes — use `WSLENV` (`WSLENV=MYVAR/u`) for any variable that should cross the WSL / Win32 boundary. Plain `export` stays on the Linux side.

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