Read private RSA key from PEM file

readkey.c

#include <stdio.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>

int main(int argc, char *argv[]) {
  FILE *f = fopen(argv[1], "r");
  RSA *key = PEM_read_RSAPrivateKey(f, NULL, NULL, NULL);
  
  RSA_print_fp(stdout, key, 0);
  fclose(f);

  return 0;
}