# 06 — Implement piping between commands

**Status:** open (post-core)
**Blocked by:** #03, #04

## Syntax

```lua
local result = `ls -l` | `grep ".lua"`
```

## Implementation

- Connect stdout of one child to stdin of the next via `pipe()` + `dup2()`
- Build a pipeline of N processes, all forked and connected
- Only capture stdout/stderr of the **final** process
- `waitpid()` all children, return exit code of last process

## Challenge

Lua uses `|` for bitwise OR. The parser needs to disambiguate:
- `|` between two command expressions → pipe
- `|` between numeric expressions → bitwise OR

This is resolvable because the parser knows the type of each subexpression — a backtick expression is always a command.