I cannot figure out how I created this file wrong

Question

I have been having trouble reading from a file I created in c with the creat system call. Here is the code:

XXXfid = creat ("XXX", 384);
    if (XXXfid<0) {printf("Error with creat"); return 0;}
    
        writeStatus = write (XXXfid, "limp", 4);
    if (writeStatus<0) {printf("error with write"); return 0;}
    lseek(XXXfid, 0, 0);
    
    readStatus = read(XXXfid, buffer, 120);
    if (readStatus<0) {printf("error with read2"); return 0;}

Every other command is working perfectly, I just can't read the file no matter what I try (ie closing and re-opening, etc). I have read and write permissions, do I need to give everyone read and write permissions? I wouldn't have thought so, given that the error I'm getting is 9- Bad File Descriptor. I'm at a total loss, any help would be appreciated I believe in octal notation my permission would be 600. If it helps, this is 110 000 000 in binary and my ls -l confirms this is -rw- --- ---

Answer 1

According to the specification:

creat(path, mode)

is equivalent to

open(path, O_WRONLY|O_CREAT|O_TRUNC, mode)

Notice that the flags contain O_WRONLY, not O_RDWR. This means you can only write to the file descriptor, not read from it.

If you want to read and write, use open() instead, with the appropriate flags.

XXXfid = open("XXX", O_RDWR | O_CREAT | O_TRUNC, 0600);