File position (counting from one) at which the target occurrence of the substr was discovered, or 0 if the target occurrence of the substr was not found.
The method also affects the state of the fd.laststatus. The following status codes are possible:
0- PL_FD_STATUS_OK: Completed successfully.
1- PL_FD_STATUS_FAIL : Physical flash memory failure (fatal).
2- PL_FD_STATUS_CHECKSUM_ERR: Checksum error has been detected in one of the disk sectors (fatal).
3- PL_FD_STATUS_FORMAT_ERR: Disk formatting error has been detected (fatal).
4- PL_FD_STATUS_INV_PARAM: Invalid argument have been provided.
8- PL_FD_STATUS_NOT_READY: The disk is not mounted.