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Piping Input to Forge

Forge supports reading input from stdin (standard input) via piping, allowing you to pass content from other commands or files directly to Forge.

Basic Usage​

Pipe content from any command or file directly to Forge:

# Pipe from echo
echo "Explain what this project does" | forge

# Using here-string (alternative syntax)
forge <<< "Explain what this project does"

# Pipe from a file
cat prompt.txt | forge

# Pipe from git commands
git log --oneline -10 | forge

# Pipe from other tools
tail -n 100 error.log | forge
cargo test 2>&1 | forge

How It Works​

When you pipe content to Forge:

  1. Detects Piped Input: Automatically recognizes stdin from a pipe
  2. Reads and Processes: Reads all content until EOF, trims whitespace, and uses it as your prompt

Critical Behavior​

--prompt Flag Takes Precedence​

Cannot Combine Piping with --prompt

The --prompt flag will completely ignore piped content:

# The piped content is IGNORED
echo "This is ignored" | forge --prompt "This is used"

Choose one input method or the other.

Works with Other Flags​

Piping works with all other Forge flags:

echo "Review this code" | forge --verbose --restricted
forge <<< "Quick task" --agent muse
git log -5 | forge --model claude-sonnet-4

Practical Examples​

Code Review Workflow​

# Simple review
echo "Review this PR: $(git diff main)" | forge

# Review staged changes
echo "Review staged changes: $(git diff --cached)" | forge

# Using here-string
forge <<< "Review this PR: $(git diff main)"

Log Analysis​

# Analyze recent errors
tail -n 50 application.log | forge

# Add context
echo "Summarize these test failures: $(cargo test 2>&1)" | forge

File Content Review​

# Review a specific file
cat src/main.rs | forge

# Review with instructions
echo "Review this code for best practices: $(cat src/database.js)" | forge

Command Output Analysis​

# Analyze directory structure
echo "Explain this directory structure: $(ls -la)" | forge

# Clipboard to Forge (macOS)
pbpaste | forge

# Clipboard to Forge (Linux with xclip)
xclip -selection clipboard -o | forge

Advanced Patterns​

Conditional Piping​

# Check file size before piping
[ -s file.txt ] && cat file.txt | forge

# Check command success
git diff --quiet || git diff | forge

Multi-Source Input​

# Combine multiple sources
echo "Current changes: $(git diff)

Recent commits: $(git log --oneline -5)

Please summarize recent development activity" | forge

Using Here-Documents​

# Multi-line prompt with command output
forge << EOF
Review these changes:

$(git diff main)

Focus on security and performance.
EOF

Tips​

  1. Don't Mix Input Methods: The --prompt flag ignores piped content. Use one or the other.
  2. Use Command Substitution: echo "Context: $(command)" | forge ensures you always have content.
  3. Mind Large Files: Piped content is read entirely into memory.
  4. Capture Errors: Use 2>&1 to capture both stdout and stderr.