RTF Rich Text Format

SIGNATURE = bytes.fromhex("7b5c727466")
OFFSET = 0

def is_rtf(path: str) -> bool:
    with open(path, "rb") as f:
        f.seek(OFFSET)
        head = f.read(len(SIGNATURE))
    return head == SIGNATURE

const SIGNATURE = [0x7b, 0x5c, 0x72, 0x74, 0x66];
const OFFSET = 0;

// bytes: a Uint8Array / Buffer holding the start of the file
export function isRtf(bytes) {
  return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}

package fileid

import "bytes"

var isrtfSignature = []byte{0x7b, 0x5c, 0x72, 0x74, 0x66}

const isrtfOffset = 0

func IsRtf(b []byte) bool {
	end := isrtfOffset + len(isrtfSignature)
	if len(b) < end {
		return false
	}
	return bytes.Equal(b[isrtfOffset:end], isrtfSignature)
}

const SIGNATURE: &[u8] = &[0x7b, 0x5c, 0x72, 0x74, 0x66];
const OFFSET: usize = 0;

fn is_rtf(bytes: &[u8]) -> bool {
    bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}

<?php
$signature = "\x7b\x5c\x72\x74\x66";
$offset = 0;

function is_rtf(string $bytes): bool {
    global $signature, $offset;
    return substr($bytes, $offset, strlen($signature)) === $signature;
}