db6f39a2a4
Defines syntax decisions and implementation plan across 7 issues:
- backtick command execution returning {code, stdout, stderr}
- ${expr} interpolation in backticks
- $SIGIL env var read/write
- argv parsing, piping, and redirection (future)
26 lines
727 B
Markdown
26 lines
727 B
Markdown
# 06 — Implement piping between commands
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**Status:** open (post-core)
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**Blocked by:** #03, #04
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## Syntax
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```lua
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local result = `ls -l` | `grep ".lua"`
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```
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## Implementation
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- Connect stdout of one child to stdin of the next via `pipe()` + `dup2()`
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- Build a pipeline of N processes, all forked and connected
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- Only capture stdout/stderr of the **final** process
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- `waitpid()` all children, return exit code of last process
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## Challenge
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Lua uses `|` for bitwise OR. The parser needs to disambiguate:
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- `|` between two command expressions → pipe
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- `|` between numeric expressions → bitwise OR
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This is resolvable because the parser knows the type of each subexpression — a backtick expression is always a command.
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