# `gno.land/p/moul/x/plan9/ns/v0`

**A Plan 9 namespace**: a private, mutable mount table over
[`ninep`](../../ninep/v0) file trees, with `bind(2)`'s flags and union
directories.

```go
import ns "gno.land/p/moul/x/plan9/ns/v0"

n := ns.New(fs.Root())
n.Bind("/usr/glenda/bin", "/bin", ns.MAFTER|ns.MCREATE)
n.ReadDir("/bin", false)   // the concatenation of both directories
```

This is the idea the rest of the suite exists for. Plan 9's leverage does not
come from "everything is a file", it comes from every process owning its own
name-to-resource mapping, so a name can be *replaced* and any service can be
composed, shadowed, sandboxed or mocked without the program knowing. Gno has one
global tree of realm paths that looks the same to everybody; an `Ns` is a view
of it that belongs to you.

**Flags follow [`bind(2)`](http://man.cat-v.org/plan_9/2/bind):** `MREPL`
replaces, `MBEFORE` splices the new directory in front of the old one, `MAFTER`
behind it, and `MCREATE` (OR'd onto any of them) marks the union member that new
files are created in.

Four Plan 9 properties are load-bearing and reproduced deliberately:

- **A union is top level only.** Binding `/a` onto `/b` unions the two
  directories at `/b`; `/b/c` resolves in whichever member won the walk and is
  not itself a union unless something is bound there too.
- **A bind captures a channel, not a name.** The source is resolved once, at
  bind time, and the file it named is what gets stored. Rebinding the source
  afterwards does not retroactively move the target.
- **A listing is a concatenation**, duplicates and all, so shadowing stays
  visible. Pass `unique` to collapse it first-wins instead.
- **Creating in a union needs `MCREATE` on some member**, and is refused
  otherwise. A plain, unbound directory takes creates with no flag at all.
- **The target of a bind must already exist**, exactly as `bind(1)` requires.

`MaxUnion` (8), `MaxOps` (64) and `ninep.MaxDepth` (32) bound resolution,
because each element of each member can cost a cross-realm call.

`String()` prints the namespace in `ns(1)` format: one line per binding, in
application order, then the working directory.

**Live demo:** [`r/moul/x/plan9/ns`](../../../../../r/moul/x/plan9/ns/v0) gives
every account one of these. Design and analysis:
[moul/gno-contracts#136](https://github.com/moul/gno-contracts/issues/136).


---

**Not affiliated with Plan 9.** Plan 9 from Bell Labs is the work of the
Computing Science Research Center at Bell Labs; the name and the marks are
theirs, and the copyright is held by the [Plan 9 Foundation](https://p9f.org).
This package borrows the vocabulary and none of the code: it is an independent
homage, asking what that ecosystem's spirit looks like on a chain. Full
attribution: [NOTICE](../../../../../NOTICE.md).

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Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

**Dependency graph:**

![gno.land/p/moul/x/plan9/ns/v0 dependency graph](https://raw.githubusercontent.com/moul/gno-contracts/main/_assets/gno.land/p/moul/x/plan9/ns/v0/deps.png)

> 🧪 **Highly experimental — potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).

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