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Write a Node.js command-line tool that processes a large text file (a log or CSV) WITHOUT loading it into memory: read it as a stream, transform each line through a Transform stream (filter/map/count), and write results to stdout or an output file. Parse arguments from process.argv, follow Unix conventions (read stdin when piped, meaningful exit codes), and fail gracefully on a missing or unreadable file.
Uses streams end to end (createReadStream + pipeline); never buffers the whole file; backpressure respected.
Parses process.argv; reads stdin when piped; correct exit codes; usage/help on bad input.
Missing/unreadable file and stream errors are caught and reported clearly, not an uncaught crash.
Small readable functions; no blocking *Sync calls on the hot path.
Use this README structure to make the work reviewable.
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# Build a streaming line-processing CLI ## Goal Write a Node.js command-line tool that processes a large text file (a log or CSV) WITHOUT loading it into memory: read it as a stream, transform each line through a Transform stream (filter/map/count), and write results to stdout or an output file. Parse arguments from process.argv, follow Unix conventions (read stdin when piped, meaningful exit codes), and fail gracefully on a missing or unreadable file. ## Acceptance criteria - [ ] Streaming: Uses streams end to end (createReadStream + pipeline); never buffers the whole file; backpressure respected. - [ ] CLI conventions: Parses process.argv; reads stdin when piped; correct exit codes; usage/help on bad input. - [ ] Error handling: Missing/unreadable file and stream errors are caught and reported clearly, not an uncaught crash. - [ ] Code quality: Small readable functions; no blocking *Sync calls on the hot path. ## Verification - [ ] Document installation and run commands. - [ ] Record automated checks and their exact commands. - [ ] Add representative output, screenshots, or a short demo where useful. - [ ] Confirm failure paths and known constraints. ## Decision log ### Decision title - Context: - Choice: - Alternatives considered: - Tradeoffs: ## Evidence - Link each rubric criterion to the file, test, or artifact that demonstrates it. ## Known limitations - List what is intentionally out of scope and what should be improved next.