Hi Ed,
> I have a question about opening the same file twice. I am finding that
> I can open the same file twice, unless I first open it for read-only
> access, and the try and open it for read-write access.
>
> The code below demonstrates. Do I have it correctly? Does the same
> rule apply for parallel situation? (That is, does the writer always
> have to open the file first?)
Yes. Since the library uses only one system call to open the file, it can't
"upgrade" a read-only file to one that permits writing.
Quincey
> Thanks!
>
> Ed
>
>
> /* Confirm that the same file can be opened twice at the same time,
> * for read only access. */
> if ((fileid = H5Fopen(FILE_NAME, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0) ERR;
> if ((fileid2 = H5Fopen(FILE_NAME, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0) ERR;
> if (H5Fclose(fileid) < 0) ERR;
> if (H5Fclose(fileid2) < 0) ERR;
>
> /* Once open for read only access, the file can't be opened again
> * for write access. */
> if ((fileid = H5Fopen(FILE_NAME, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0) ERR;
> if ((fileid2 = H5Fopen(FILE_NAME, H5F_ACC_RDWR, H5P_DEFAULT)) >= 0) ERR;
> if (H5Fclose(fileid) < 0) ERR;
>
> /* But you can open the file for read/write access, and then open
> * it again for read only access. */
> if ((fileid2 = H5Fopen(FILE_NAME, H5F_ACC_RDWR, H5P_DEFAULT)) < 0) ERR;
> if ((fileid = H5Fopen(FILE_NAME, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0) ERR;
> if (H5Fclose(fileid) < 0) ERR;
> if (H5Fclose(fileid2) < 0) ERR;
>
>
>
> --
> Ed Hartnett -- ed@xxxxxxxxxxxxxxxx
>
