read_file

The read_file tool examines the contents of files in a project. It allows Roo to understand code, configuration files, and documentation to provide better assistance.

Parameters

The tool accepts these parameters:

• path (required): The path of the file to read relative to the current working directory
• start_line (optional): The starting line number to read from (1-based indexing)
• end_line (optional): The ending line number to read to (1-based, inclusive)
• auto_truncate (optional): Whether to automatically truncate large files when line range isn't specified (true/false)

What It Does

This tool reads the content of a specified file and returns it with line numbers for easy reference. It can read entire files or specific sections, and even extract text from PDFs and Word documents.

When is it used?

• When Roo needs to understand existing code structure
• When Roo needs to analyze configuration files
• When Roo needs to extract information from text files
• When Roo needs to see code before suggesting changes
• When specific line numbers need to be referenced in discussions

Key Features

• Displays file content with line numbers for easy reference
• Can read specific portions of files by specifying line ranges
• Extracts readable text from PDF and DOCX files
• Intelligently truncates large files to focus on the most relevant sections
• Provides method summaries with line ranges for large code files
• Efficiently streams only requested line ranges for better performance
• Makes it easy to discuss specific parts of code with line numbering

Limitations

• May not handle extremely large files efficiently without using line range parameters
• For binary files (except PDF and DOCX), may return content that isn't human-readable

How It Works

When the read_file tool is invoked, it follows this process:

1. Parameter Validation: Validates the required path parameter and optional parameters
2. Path Resolution: Resolves the relative path to an absolute path
3. Reading Strategy Selection:
   • The tool uses a strict priority hierarchy (explained in detail below)
   • It chooses between range reading, auto-truncation, or full file reading
4. Content Processing:
   • Adds line numbers to the content (e.g., "1 | const x = 13") where 1 | is the line number.
   • For truncated files, adds truncation notice and method definitions
   • For special formats (PDF, DOCX, IPYNB), extracts readable text

Reading Strategy Priority

The tool uses a clear decision hierarchy to determine how to read a file:

1. First Priority: Explicit Line Range

   • If either start_line or end_line is provided, the tool always performs a range read
   • The implementation efficiently streams only the requested lines, making it suitable for processing large files
   • This takes precedence over all other options

2. Second Priority: Auto-Truncation for Large Files

   • This only applies when ALL of these conditions are met:
     • Neither start_line nor end_line is specified
     • The auto_truncate parameter is set to true
     • The file is not a binary file
     • The file exceeds the configured line threshold (typically 500-1000 lines)
   • When auto-truncation activates, the tool:
     • Reads only the first portion of the file (determined by the maxReadFileLine setting)
     • Adds a truncation notice showing the number of lines displayed vs. total
     • Provides a summary of method definitions with their line ranges

3. Default Behavior: Read Entire File

   • If neither of the above conditions are met, it reads the entire file content
   • For special formats like PDF, DOCX, and IPYNB, it uses specialized extractors

Examples When Used

• When asked to explain or improve code, Roo first reads the relevant files to understand the current implementation.
• When troubleshooting configuration issues, Roo reads config files to identify potential problems.
• When working with documentation, Roo reads existing docs to understand the current content before suggesting improvements.

Usage Examples

Reading an entire file:

<read_file>
<path>src/app.js</path>
</read_file>

Reading specific lines (46-68) of a file:

<read_file>
<path>src/app.js</path>
<start_line>46</start_line>
<end_line>68</end_line>
</read_file>

Reading a large file with auto-truncation:

<read_file>
<path>src/large-module.js</path>
<auto_truncate>true</auto_truncate>
</read_file>