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Appendix B: Command Reference

This appendix provides a comprehensive reference for all command-line options and usage patterns of the rmagic tool.

Command Syntax

rmagic [OPTIONS] <FILE>...

Options

Basic Options

<FILE>

  • Type: Positional argument (required)
  • Description: Path to the file(s) to analyze
  • Multiple: Yes, can specify multiple files
  • Examples: 
    rmagic file.bin
rmagic file1.exe file2.pdf file3.zip
rmagic /path/to/directory/*

--help, -h

  • Description: Display help information and exit
  • Example: 
    rmagic --help

--version, -V

  • Description: Display version information and exit
  • Example: 
    rmagic --version

Output Format Options

--json

  • Description: Output results in JSON format instead of text
  • Default: Text format
  • Example: 
    rmagic --json file.bin
  • Output Example: 
    {
  "filename": "file.bin",
  "description": "ELF 64-bit LSB executable",
  "mime_type": "application/x-executable",
  "confidence": 1.0
}

--text

  • Description: Output results in text format (default behavior)
  • Default: Enabled
  • Example: 
    rmagic --text file.bin
# Output: file.bin: ELF 64-bit LSB executable

Magic Database Options

--magic-file <FILE>

  • Description: Use a custom magic file instead of the default
  • Type: Path to magic file
  • Default: Built-in magic database
  • Example: 
    rmagic --magic-file custom.magic file.bin
rmagic --magic-file /usr/share/misc/magic file.bin

Advanced Options (Planned)

--mime-type, -i

  • Description: Output MIME type instead of description
  • Status: 📋 Planned
  • Example: 
    rmagic --mime-type file.bin
# Output: application/x-executable

--mime-encoding, -e

  • Description: Output MIME encoding
  • Status: 📋 Planned
  • Example: 
    rmagic --mime-encoding text.txt
# Output: us-ascii

--brief, -b

  • Description: Brief output (no filename prefix)
  • Status: 📋 Planned
  • Example: 
    rmagic --brief file.bin
# Output: ELF 64-bit LSB executable

--raw, -r

  • Description: Raw output (no pretty formatting)
  • Status: 📋 Planned

--follow-symlinks, -L

  • Description: Follow symbolic links
  • Status: 📋 Planned

--no-follow-symlinks, -h

  • Description: Don't follow symbolic links (default)
  • Status: 📋 Planned

--compress, -z

  • Description: Try to look inside compressed files
  • Status: 📋 Planned

--uncompress, -Z

  • Description: Try to look inside compressed files (same as -z)
  • Status: 📋 Planned

--exclude <PATTERN>

  • Description: Exclude files matching pattern
  • Status: 📋 Planned

--include <PATTERN>

  • Description: Only include files matching pattern
  • Status: 📋 Planned

Usage Examples

Basic File Identification

# Single file
rmagic document.pdf
# Output: document.pdf: PDF document, version 1.4

# Multiple files
rmagic *.bin
# Output:
# file1.bin: ELF 64-bit LSB executable
# file2.bin: data
# file3.bin: PNG image data, 1920 x 1080, 8-bit/color RGBA

JSON Output

# Single file JSON output
rmagic --json executable.elf

{
  "filename": "executable.elf",
  "description": "ELF 64-bit LSB executable, x86-64, version 1 (SYSV)",
  "mime_type": "application/x-executable",
  "confidence": 1.0,
  "matches": [
    {
      "offset": 0,
      "rule": "ELF magic",
      "value": "7f454c46",
      "message": "ELF"
    },
    {
      "offset": 4,
      "rule": "ELF class",
      "value": "02",
      "message": "64-bit"
    }
  ]
}

Custom Magic Files

# Use custom magic database
rmagic --magic-file /path/to/custom.magic file.bin

# Use multiple magic files (planned)
rmagic --magic-file magic1.db --magic-file magic2.db file.bin

Batch Processing

# Process all files in directory
rmagic /path/to/files/*

# Process with JSON output for scripting
rmagic --json /path/to/files/* > results.json

# Process recursively (planned)
rmagic --recursive /path/to/directory/

Exit Codes

CodeMeaning
0Success - all files processed successfully
1Error - general error (file not found, permission denied, etc.)
2Usage error - invalid command line arguments
3Magic file error - invalid or missing magic file

Environment Variables

MAGIC

  • Description: Default magic file path
  • Default: Built-in magic database
  • Example: 
    export MAGIC=/usr/local/share/magic
rmagic file.bin  # Uses /usr/local/share/magic

RMAGIC_DEBUG

  • Description: Enable debug output
  • Values: 0 (off), 1 (basic), 2 (verbose)
  • Example: 
    RMAGIC_DEBUG=1 rmagic file.bin

Configuration Files (Planned)

Global Configuration

  • Path: /etc/rmagic.conf
  • Format: TOML
  • Purpose: System-wide defaults

User Configuration

  • Path: ~/.config/rmagic/config.toml
  • Format: TOML
  • Purpose: User-specific settings

Example Configuration

[output]
format = "json"
brief = false

[magic]
default_file = "/usr/local/share/magic"
search_paths = [
  "/usr/share/misc/magic",
  "/usr/local/share/magic",
  "~/.local/share/magic",
]

[performance]
max_file_size = "100MB"
timeout = "30s"

Compatibility with GNU file

The rmagic command aims for compatibility with GNU file command:

Compatible Options

  • Basic file analysis
  • JSON output format
  • Custom magic file specification
  • Multiple file processing

Differences

  • JSON output format may differ in structure
  • Some advanced GNU file options not yet implemented
  • Performance characteristics may vary
  • Error messages may differ

Migration Guide

# GNU file command
file -i document.pdf
file --mime-type document.pdf

# rmagic equivalent (planned)
rmagic --mime-type document.pdf
rmagic -i document.pdf

Performance Considerations

Large Files

  • Files are memory-mapped for efficiency
  • Only necessary portions are read
  • Configurable size limits prevent excessive memory usage

Batch Processing

  • Multiple files processed efficiently
  • Parallel processing planned for future versions
  • Progress reporting for large batches

Memory Usage

  • Constant memory usage regardless of file size
  • Magic database cached in memory
  • Minimal allocations during evaluation

Troubleshooting

Common Issues

"File not found"

rmagic nonexistent.file
# Error: File not found: nonexistent.file

Solution: Check file path and permissions

"Permission denied"

rmagic /root/private.file
# Error: Permission denied: /root/private.file

Solution: Check file permissions or run with appropriate privileges

"Invalid magic file"

rmagic --magic-file broken.magic file.bin
# Error: Parse error in magic file at line 42: Invalid offset specification

Solution: Validate magic file syntax

Debug Mode

# Enable debug output
RMAGIC_DEBUG=1 rmagic file.bin

# Verbose debug output
RMAGIC_DEBUG=2 rmagic file.bin

This command reference provides comprehensive documentation for all current and planned features of the rmagic command-line tool.