How to read and write a file

Reading transfers data from a file to a descriptor, and writing transfers data from a descriptor to a file.

Use RFile::Read() to read, and RFile::Write() to write.

// Open file1
_LIT(KMyFile,"c:\\documents\\file1");
RFile myFile;
User::LeaveIfError(myFile.Open(fs,KMyFile,EFileShareExclusive|EFileWrite
));

// Write to current file position: start of file
_LIT8(KWriteBuf,"write data");
myFile.Write(KWriteBuf);

// Read from position 0: start of file
TBuf8<6> readBuf1;
myFile.Read(0,readBuf1); // readBuf1 is now "write "

// Read from current position
TBuf8<4> readBuf2;
myFile.Read(readBuf2);    // readBuf2 is now "data"

Notes

In all cases, the file data is treated as binary and byte descriptors are used (TDes8, TDesC8). Thus, file operations are not dependent on the Unicode/non-Unicode build variant.
There are several variants of both Read() and Write(). The basic Read(TDes8& aDes) and Write(const TDesC8& aDes) are supplemented by variants allowing the descriptor length to be overridden, or the seek position of the first byte to be specified, or asynchronous completion, or any combination.