Last modified: 9 October 2014
Name: H5Fopen
Signature:
  hid_t `H5Fopen`( const char *`name`, unsigned `flags`, hid_t `fapl_id` )

Purpose:
  Opens an existing HDF5 file.

Description:
  `H5Fopen` is the primary function for accessing existing HDF5 files. This function opens the named file in the specified access mode and with the specified access property list.

  Note that `H5Fopen` does not create a file if it does not already exist; see `H5Fcreate`.

  The `name` parameter specifies the name of the file to be opened.

  The `fapl_id` parameter specifies the file access property list. Use of `H5P_DEFAULT` specifies that default I/O access properties are to be used

  The `flags` parameter specifies whether the file will be opened in read-write or read-only mode, `H5F_ACC_RDWR` or `H5F_ACC_RDONLY`, respectively. More complex behaviors of file access are controlled through the file-access property list.

  The return value is a file identifier for the open file; this file identifier should be closed by calling `H5Fclose` when it is no longer needed.

  Special cases — Multiple opens:
  A file can often be opened with a new `H5Fopen` call without closing an already-open identifier established in a previous `H5Fopen` or `H5Fcreate` call. Each such `H5Fopen` call will return a unique identifier and the file can be accessed through any of these identifiers as long as the identifier remains valid. In such multiply-opened cases, the open calls must use the same `flags` argument and the file access property lists must use the same file close degree property setting (see the external link discussion below and `H5Pset_fclose_degree`).

  In some cases, such as files on a local Unix file system, the HDF5 library can detect that a file is multiply opened and will maintain coherent access among the file identifiers.

  But in many other cases, such as parallel file systems or networked file systems, it is not always possible to detect multiple opens of the same physical file. In such cases, HDF5 will treat the file identifiers as though they are accessing different files and will be unable to maintain coherent access. Errors are likely to result in these cases. While unlikely, the HDF5 library may not be able to detect, and thus report, such errors.

  It is generally recommended that applications avoid multiple opens of the same file.

  Special restriction on multiple opens of a file first opened by means of an external link: When an external link is followed, the external file is always opened with the weak file close degree property setting, `H5F_CLOSE_WEAK` (see `H5Lcreate_external` and `H5Pset_fclose_degree`). If the file is reopened with `H5Fopen` while it remains held open from such an external link call, the file access proeprty list used in the open call must include the file close degree setting `H5F_CLOSE_WEAK` or the open will fail.

Parameters:

  const char *`name` | IN: Name of the file to be opened.
  unsigned `flags` | IN: File access flags. Allowable values are: `H5F_ACC_RDWR` Allow read and write access to file. `H5F_ACC_RDONLY` Allow read-only access to file. `H5F_ACC_RDWR` and `H5F_ACC_RDONLY` are mutually exclusive; use exactly one. An additional flag, `H5F_ACC_DEBUG`, prints debug information. This flag can be combined with one of the above values using the bit-wise OR operator (`|'), but it is used only by HDF5 Library developers; it is neither tested nor supported for use in applications.
  hid_t `fapl_id` | IN: Identifier for the file access properties list. If parallel file access is desired, this is a collective call according to the communicator stored in the `fapl_id`. Use `H5P_DEFAULT` for default file access properties.

Returns:
  Returns a file identifier if successful; otherwise returns a negative value.

Fortran90 Interface: h5fopen_f

      SUBROUTINE h5fopen_f(name, access_flags, file_id, hdferr, &
                           access_prp)
        IMPLICIT NONE
        CHARACTER(LEN=*), INTENT(IN) :: name   ! Name of the file
        INTEGER, INTENT(IN) :: access_flag     ! File access flags
                                               ! Possible values are:
                                               !     H5F_ACC_RDWR_F
                                               !     H5F_ACC_RDONLY_F
        INTEGER(HID_T), INTENT(OUT) :: file_id ! File identifier
        INTEGER, INTENT(OUT) :: hdferr         ! Error code
                                               ! 0 on success and -1 on failure
        INTEGER(HID_T), OPTIONAL, INTENT(IN) :: access_prp
                                               ! File access property list
                                               ! identifier
      END SUBROUTINE h5fopen_f

See Also:
  “Using Identifiers”