# Generate a Hundred Files from One Template

![banner](https://articles.aux4.blog/data/posts/aux4/generate-a-hundred-files-from-one-template/banner.png)

## Introduction

Onboarding letters, per-service config files, a reference table that must match the schema — all of it gets hand-written, and all of it drifts the moment the data changes. This post keeps the facts in one data file and *generates* the files from a template: a personalized file per record, or a single doc rolled up from structured data. Edit the data, re-run, done.

## Install the packages

```bash
aux4 aux4 pkger install aux4/template aux4/json
```

## Step 1: a template and one render

`aux4/template` renders [Handlebars](https://handlebarsjs.com). Any `--key value` flag becomes a template variable. Create `welcome.hbs`:

```handlebars
Hi {{name}},

Welcome aboard as our new {{role}}! Your first day is {{start}}.

— The Team
```

Render one:

```bash
aux4 template --file welcome.hbs --name Sally --role Engineer --start 2026-08-01
```

```text
Hi Sally,

Welcome aboard as our new Engineer! Your first day is 2026-08-01.

— The Team
```

## Step 2: one file per record — the hundred files

Put the data in a file — `people.json`, a list of records:

```json
[
  { "name": "Sally", "role": "Engineer", "start": "2026-08-01" },
  { "name": "Marco", "role": "Designer", "start": "2026-08-04" },
  { "name": "Priya", "role": "PM",       "start": "2026-08-06" }
]
```

Now run the template once per record with `aux4 json exec`, writing each result to its own file. `${item.field}` is the current record's field, and `--output` names the file:

```bash
cat people.json | aux4 json exec 'aux4 template --file welcome.hbs --name "${item.name}" --role "${item.role}" --start "${item.start}" --output "${item.name}.txt"'
```

Three records in, three files out — no loop, no scripting:

```bash
ls *.txt
```

```text
Marco.txt
Priya.txt
Sally.txt
```

```bash
cat Sally.txt
```

```text
Hi Sally,

Welcome aboard as our new Engineer! Your first day is 2026-08-01.

— The Team
```

Ten records make ten files; ten thousand make ten thousand. The template never changes — only the data does.

## Step 3: a single doc from structured data

The same tool rolls many records *into one* file. For a document like an API reference, put the records under a key and iterate them with `{{#each}}`. Create `api.json`:

```json
{
  "endpoints": [
    { "name": "List users",   "method": "GET",  "path": "/users",  "description": "Return all users.", "auth": true },
    { "name": "Create user",  "method": "POST", "path": "/users",  "description": "Create a new user.", "auth": true },
    { "name": "Health check", "method": "GET",  "path": "/health", "description": "Liveness probe.",    "auth": false }
  ]
}
```

And `reference.hbs` — note `{{#if auth}}` reads the real JSON boolean:

```handlebars
# API Reference

| Name | Method | Path | Auth |
| --- | --- | --- | --- |
{{#each endpoints}}
| {{name}} | `{{method}}` | `{{path}}` | {{#if auth}}Yes{{else}}No{{/if}} |
{{/each}}
```

Pass the whole file as the context with `--data` and get a finished Markdown table:

```bash
aux4 template --file reference.hbs --data api.json
```

```text
# API Reference

| Name | Method | Path | Auth |
| --- | --- | --- | --- |
| List users | `GET` | `/users` | Yes |
| Create user | `POST` | `/users` | Yes |
| Health check | `GET` | `/health` | No |
```

Add `--output REFERENCE.md` to write it to a file, wire that into an `.aux4` command (`aux4 docs generate`), and your reference is regenerated from the source of truth every time — it can't go stale, because nobody edits the Markdown by hand.

## Conclusion

`aux4/template` turns data into files: `aux4 json exec` fans a template out to one file per record, and `--data` with `{{#each}}` rolls records up into a single document. The facts live in one place; the files are always a re-run away. Onboarding letters, config files, invoices, docs — write the template once and generate the rest.

## See Also

- [aux4/template](https://hub.aux4.io/r/public/packages/aux4/template)
- [aux4/json](https://hub.aux4.io/r/public/packages/aux4/json)