Parse JSON from a shell

curl -s api.example.com/me | jq -r '.email'

**`-r` is the field that makes jq a pipe-able tool** — without it, jq emits JSON-quoted strings (`"[email protected]"` with literal quotes), so `mail $(jq .email)` sends to the wrong address. With `-r` (raw output): `[email protected]`. The selector DSL: `.field` (one key), `.field.subfield` (nested), `.items[]` (iterate array), `.items[0]` (index), `.items | length` (count), `.items[] | select(.active)` (filter), `.users[] | "\(.name) <\(.email)>"` (string-interpolate). For injecting shell variables INTO a jq filter, NEVER concatenate (injection risk): use `--arg` for strings (`jq --arg u "$USER" '.users[] | select(.name==$u)'`) or `--argjson` for non-string values (`jq --argjson n 5 '.items[$n]'`).

curl -s api.example.com/me | jq -r '.email'

Same external `jq`. Install: `brew install jq` (macOS), `apt install jq` (Debian/Ubuntu), `apk add jq` (Alpine). For "if jq is not installed" graceful fallback: `python3 -c "import sys,json; print(json.load(sys.stdin)['email'])"` works on virtually every Linux/macOS box. For YAML/TOML, `yq` (Python rewrite) extends jq syntax to other formats — same `-r` flag. `jaq` is a Rust rewrite of jq with the same query language — faster on large files but not always packaged in distros.

curl -s api.example.com/me | jq -r '.email'

Same external. Fish-native interpolation makes jq pipelines tidy: `set email (curl -s api.example.com/me | jq -r .email); echo "got: $email"`. Fish doesn't need the bash `$(...)` subshell syntax — `(...)` is the same idea, cleaner inside double-quoted strings. For "extract many fields at once into separate vars": `set name email (curl -s … | jq -r ".name, .email")` — jq emits one value per line; fish `set` with multiple names splits by newline.

(Invoke-RestMethod api.example.com/me).email

Pwsh skips the jq middleman — `Invoke-RestMethod` auto-deserializes JSON to nested PowerShell objects, then normal dot access works (`.email`, `.users[0].email`, `.items.Where({$_.active})`). For STRING-input JSON: `$json | ConvertFrom-Json`. **The #1 footgun: pwsh property access is CASE-INSENSITIVE by default** (`$obj.EMAIL` and `$obj.email` both work) — JSON spec says keys are case-sensitive. If your JSON has both `Id` and `id` keys, default `[PSCustomObject]` SILENTLY COLLAPSES them; use `-AsHashtable` (pwsh 6+) to preserve case-sensitivity: `$json | ConvertFrom-Json -AsHashtable`. For "one specific field, raw string out": just dot-access — no quoting issue like jq has (since pwsh strings have no implicit quotes). For "filter then extract": `($json | ConvertFrom-Json).items | Where-Object active | ForEach-Object email`.

for /f %i in ('powershell -NoProfile -Command "(Invoke-RestMethod api.example.com/me).email"') do set EMAIL=%i

cmd has NO native JSON parser. The portable answer is to shell out to pwsh (above) and capture via `for /f`. Watch the quote-escaping: cmd's `for /f` parses the pwsh output by whitespace (one token per line); `delims=` disables tokenization for full-line capture. If jq is installed on Windows (`winget install jqlang.jq`): `curl -s api.example.com/me | jq -r ".email"` works in cmd too — same syntax as bash. For a one-shot lookup, just run the pwsh command directly; for a `.bat` that needs the value: the `for /f` capture pattern.