Question

Having few issues with my copy program which creates a copy of a file user enteres. I decided not to use (size_t) structure instead just assigned (int) and (char) types variables so I know exact value of bytes to read() out. ie I know start at beggining of file and read 4 bytes(int) to get value of lenght of filename, which I use as size in next read()

So, when I am writing (copying file exactly with same name) users inputted file to the output file (copied file) I writing it in long string, without spaces obviously just to make it readable here,

filenamesize filename filecontentsize filecontent
ie 10 myfile.txt 5 hello

So when come to reading that data out I start at begining of file using lseek() and I know the first 4 bytes are (int) which is lenght of filename so I put that into value int namelen using the read function.

My problem is I want to use that value read for the filenamesize(first 4 bytes) to declare my array to store filename with the right lenght. How do I put this array into read() so the read stores value inside that char array specified, see below please

int namelen; //value read from first 4 bytes of file lenght of filename to go in nxt read()
char filename[namelen]; 
read(fd, filename[namelen], namelen);//filename should have 'myfile.txt' if user entered that filename

So my question is once I read that first 4 bytes from file giving me lenght of filename stored in namelen, I then want to read namelen amount of bytes to give me the filename of originally file so I can create copied file inside directory?

Thanks

Answer 1

int namelen; //value read from first 4 bytes of file lenght of filename to go in nxt read()
char* filename = new char[namelen+1]; 
read(fd, filename, namelen);
filename[namelen]=0; // Just to keep readed buffer c-string compatible
do something with filename
delete[] filename;