#!/usr/bin/env python3
"""SHA256 file hash calculator - quick utility for integrity verification."""
import hashlib
import sys
from pathlib import Path

def calc_sha256(file_path: str) -> str:
    """Calculate SHA256 hash of a file."""
    h = hashlib.sha256()
    with open(file_path, 'rb') as f:
        for chunk in iter(lambda: f.read(8192), b''):
            h.update(chunk)
    return h.hexdigest()

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print("Usage: sha256_tool.py <file>", file=sys.stderr)
        sys.exit(1)
    
    path = Path(sys.argv[1])
    if not path.exists():
        print(f"Error: {path} not found", file=sys.stderr)
        sys.exit(1)
    
    print(calc_sha256(str(path)))