file-to-base64

File to Base64 Converter

This skill converts files to Base64-encoded strings and detects their MIME types, which is essential for attaching files to FreeAgent expenses, timeslips, and other API operations that require file uploads.

When to Use This Skill

Use this skill when:

• Preparing attachments for FreeAgent API calls (expenses, timeslips)
• Converting PDFs or images to Base64 format
• Detecting MIME types for file uploads
• Validating file formats and sizes for API requirements

Supported File Formats

FreeAgent Supported Formats

• PDF (.pdf) - application/pdf
• PNG (.png) - image/png
• JPEG (.jpg, .jpeg) - image/jpeg
• GIF (.gif) - image/gif

Additional Common Formats (for reference)

• Text files (.txt) - text/plain
• Word documents (.doc, .docx)
• Excel files (.xls, .xlsx)

File Size Limits

• FreeAgent API: Maximum 5MB per file

How to Use

1. Convert a Single File

# Read the file and convert to Base64
base64 /path/to/file.pdf

# Get MIME type from extension
# For .pdf -> application/pdf
# For .png -> image/png
# For .jpg/.jpeg -> image/jpeg
# For .gif -> image/gif

2. Check File Size

# Check file size in bytes
stat -f%z /path/to/file.pdf  # macOS
stat -c%s /path/to/file.pdf  # Linux

# Convert to MB for comparison
# 5MB = 5242880 bytes

3. Validate File Before Conversion

# Check if file exists and is readable
test -r /path/to/file.pdf && echo "File is readable" || echo "Cannot read file"

# Get file extension
basename /path/to/file.pdf | sed 's/.*\.//'

Example Workflow

Prepare an Attachment for FreeAgent Expense

# 1. Validate file exists
FILE_PATH="/path/to/receipt.pdf"
test -f "$FILE_PATH" || exit 1

# 2. Check file size (must be < 5MB = 5242880 bytes)
FILE_SIZE=$(stat -f%z "$FILE_PATH")
if [ $FILE_SIZE -gt 5242880 ]; then
  echo "Error: File size exceeds 5MB limit"
  exit 1
fi

# 3. Get filename
FILE_NAME=$(basename "$FILE_PATH")

# 4. Determine MIME type from extension
EXT="${FILE_PATH##*.}"
case "$EXT" in
  pdf) MIME_TYPE="application/pdf" ;;
  png) MIME_TYPE="image/png" ;;
  jpg|jpeg) MIME_TYPE="image/jpeg" ;;
  gif) MIME_TYPE="image/gif" ;;
  *) echo "Unsupported format"; exit 1 ;;
esac

# 5. Convert to Base64
BASE64_DATA=$(base64 "$FILE_PATH")

# 6. Output in format ready for API
echo "Attachment prepared:"
echo "- file_name: $FILE_NAME"
echo "- content_type: $MIME_TYPE"
echo "- data: [Base64 string - ${#BASE64_DATA} characters]"