FUSE Filesystem Example

Question

This is in reference to hello_getattr function in hello.c, which comes as example in libfuse.

What does st_mode field signify in the code below? To be specific why are setting st_mode to specific values as shown below?

static int hello_getattr(const char *path, struct stat *stbuf,
                         struct fuse_file_info *fi)
{
        (void) fi;
        int res = 0;
        memset(stbuf, 0, sizeof(struct stat));
        if (strcmp(path, "/") == 0) {
                stbuf->st_mode = S_IFDIR | 0755;
                stbuf->st_nlink = 2;
        } else if (strcmp(path+1, options.filename) == 0) {
                stbuf->st_mode = S_IFREG | 0444;
                stbuf->st_nlink = 1;
                stbuf->st_size = strlen(options.contents);
        } else
                res = -ENOENT;
        return res;
}