Is there a random_device equivalent in C

In C++ we can generate true random numbers (if your hardware supports) with random_device. And i am writing a implementation of One-time Pad algorithm with C. Is there a way to generate true random numbers in C? I writing with C for speed and some another reasons. If i use a PRNG, it is will be unsafe.

char *KeyGenerate(unsigned long long StringLength)
{
    std::random_device TrueRandomNumberGenerator;
    char *Key = (char *) malloc(StringLength + 1);

    for(unsigned long long I = 0; I < StringLength; I++)
    {
        Key[I] = TrueRandomNumberGenerator();
    }
    Key[StringLength] = '\0';

    return Key;
}