nu-emit

Table of Contents

• Why
• Tiers (intentional)
• C sketch
• Status
• Related
• License

Small libraries so apps can emit structured rows for Nushell without hand-writing JSON strings.

Why

Nushell is happy if you print JSONL and pipe through from json. That still means every C programmer reinvents fprintf(stdout, "{\"pid\": %d…​}") and gets the commas wrong at 2am.

nu-emit is the boring fix: build a row in memory, call an API, flush. First target is C. Other languages can follow the same shape.

This is the “DevX approved” path from the Nu-vs-pwsh discussion: a real emit API, not folklore.

Tiers (intentional)

1. JSONL emit (this repo, v0) — zero coupling to Nu’s plugin protocol; works today with ./app | from json

2. Plugin protocol (later) — MsgPack/JSON IPC for native plugins when you need typed input too

Do not wait for a libnushell.so C ABI. Nu does not ship that, and chasing it before 1.0 is a trap.

C sketch

#include "nu_emit.h"

int main(void) {
    nu_emit_row_begin();
    nu_emit_field_str("status", "running");
    nu_emit_field_i64("pid", 4012);
    nu_emit_field_i64("memory_mb", 128);
    nu_emit_row_end(); /* writes one JSON object + newline, fflush */
    return 0;
}

./my_c_app | from json | where memory_mb > 100

Status

Scaffold. Headers + tiny encoder stub first; harden escaping and types next.

Related

• https://github.com/openshellorg/nu-require — require / relaunch under Nu

• https://github.com/openshellorg/shell-architecture — thesis

• https://www.nushell.sh/

License

MIT