d0181e685d
Add split_pipeline() to split command strings on unquoted | and exec_pipeline() to fork N children connected by inter-stage pipes. Only the last stage's stdout/stderr are captured; middle stages' stderr is inherited. Exit code comes from the last stage.
41 lines
1.4 KiB
Markdown
41 lines
1.4 KiB
Markdown
# 06 — Implement piping between commands
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**Status:** done
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## Syntax
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Pipes are written inside backtick strings using `|`:
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```lua
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local r = `ls -l | grep ".lua" | wc -l`
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```
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The `|` operator between backtick expressions remains Lua's bitwise OR — pipes only work *within* a single backtick command string.
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## Implementation
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Implemented in `lcmd.c` with two new functions:
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- **`split_pipeline()`** — scans the command string for `|` outside single/double quotes, splits into an array of stage strings (up to 64 stages). Reuses the same quote-tracking logic as `parse_argv()`.
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- **`exec_pipeline()`** — executes a multi-stage pipeline:
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1. `parse_argv()` each stage
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2. Creates N-1 inter-stage pipes + stdout/stderr capture pipes for the last stage
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3. Forks N children with appropriate stdin/stdout wiring
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4. Captures output from the last stage only
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5. Returns `{code=last_exit_code, stdout=captured, stderr=captured}`
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`luaB_command()` calls `split_pipeline()` first. Single-stage commands (no `|`) fall through to the original single-command codepath unchanged.
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## Behaviour
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- Exit code is from the **last** pipeline stage (like bash)
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- Only the last stage's stdout/stderr are captured in the result table
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- Middle stages' stderr is inherited (goes to terminal)
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- Quoted `|` characters (single or double quotes) are not pipe separators
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- Empty pipeline stages (e.g. `cmd1 || cmd2` or leading/trailing `|`) are errors
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## Tests
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See `testes/lush/piping.lua`.
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