Appendix B: Command Reference#

# From source
git clone https://github.com/EvilBit-Labs/libmagic-rs
cd libmagic-rs
cargo install --path .

rmagic [OPTIONS] <FILE>...
rmagic [OPTIONS] -

filename: description

document.pdf: PDF document
image.png: PNG image data
binary.exe: PE32 executable

{
  "matches": [
    {
      "message": "ELF 64-bit LSB executable",
      "offset": 0,
      "length": 4,
      "value": "7f454c46",
      "rule_path": [
        "elf",
        "executable"
      ],
      "confidence": 90,
      "mime_type": "application/x-executable"
    }
  ]
}

{"filename":"file1.bin","matches":[...]}
{"filename":"file2.bin","matches":[...]}

# Identify a single file
rmagic document.pdf

# Identify multiple files
rmagic *.bin

# Use built-in rules
rmagic --use-builtin image.png

# Read from stdin
cat unknown.bin | rmagic -

# Single file with pretty JSON
rmagic --json executable.elf

# Multiple files with JSON Lines
rmagic --json file1.bin file2.bin file3.bin

# Parse JSON output with jq
rmagic --json binary.exe | jq '.matches[0].text'

# Use specific magic file
rmagic --magic-file /path/to/custom.magic files/*

# Use magic directory (Magdir style)
rmagic --magic-file /usr/share/file/magic files/*

# Strict mode - fail on first error
rmagic --strict *.bin

# With timeout protection
rmagic --timeout-ms 5000 large-file.bin

# Combine options
rmagic --strict --timeout-ms 10000 --json *.bin

# Find all ELF files
find . -type f -exec rmagic --use-builtin {} + | grep ELF

# Process files and output JSON
for f in *.bin; do
    rmagic --json "$f" >> results.jsonl
done

# Use with xargs
find . -name "*.dat" -print0 | xargs -0 rmagic --use-builtin

#!/bin/bash
# Check if file is an image

if rmagic --use-builtin "$1" | grep -q "image"; then
    echo "File is an image"
    exit 0
else
    echo "File is not an image"
    exit 1
fi

# Solution 1: Use built-in rules
rmagic --use-builtin file.bin

# Solution 2: Specify magic file path
rmagic --magic-file /path/to/magic file.bin

# Solution 3: Check available locations
ls -la /usr/share/misc/magic /usr/share/file/magic* 2>/dev/null

# Binary .mgc files are not supported
# Use --use-builtin or a text magic file

rmagic --use-builtin file.bin

# Increase timeout
rmagic --timeout-ms 30000 large-file.bin

# Or use simpler rules
rmagic --use-builtin large-file.bin

# Check file permissions
ls -la file.bin

# Fix permissions if needed
chmod +r file.bin

# Check which magic file is being used
rmagic --help # Shows version

# Test with built-in rules first
rmagic --use-builtin test-file.bin

# Verbose error with strict mode
rmagic --strict file.bin

# Before (GNU file)
file document.pdf

# After (rmagic)
rmagic document.pdf

# With options
file -i document.pdf # MIME type
rmagic --json document.pdf | jq '.matches[0].mime_type'