// PROTOTYPE int truncate(const char* pathname, off_t length)
Truncate a file to a given length.
pathname: The pathname to the file (Unix-style, with forward slash as the directory separator).
length: length in bytes.
Returns 0 on success. On error, returns -1 and sets
errno. Some possible
errno values include:
ENOENT: File does not exist.
ENOSPCThere is no space on the file system.