---
epic: 11
story: 11.2
title: "Pipe / Stdin Mode"
status: draft
---

## Epic 11 — CLI Tool
**Goal:** Command-line tool for scripting and automation, same Rust engine.

### Story 11.2: Pipe / Stdin Mode

As a developer,
I want to pipe input into CalcPad from other commands,
So that I can integrate calculations into shell scripts and pipelines.

**Acceptance Criteria:**

**Given** the user pipes a single expression to calcpad
**When** they run `echo "100 USD in EUR" | calcpad`
**Then** the converted value is printed to stdout
**And** the process exits with code 0

**Given** the user pipes multi-line input to calcpad
**When** they run `cat mysheet.cp | calcpad` or pipe multiple lines via heredoc
**Then** each line is evaluated as part of a sheet (variables carry forward between lines)
**And** each line's result is printed on a corresponding output line

**Given** stdin contains a mix of expressions, comments, and blank lines
**When** calcpad processes the input
**Then** comments and blank lines produce empty output lines
**And** expressions produce their computed results on the corresponding lines
