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HDF5 1.14.5
API Reference
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Attributes (H5A)

Detailed Description

An HDF5 attribute is a small metadata object describing the nature and/or intended usage of a primary data object. A primary data object may be a dataset, group, or committed datatype.

See also
HDF5 Attributes

Macros

#define H5Acreate   H5Acreate2
 
#define H5Aiterate   H5Aiterate2
 

Functions

herr_t H5Aclose (hid_t attr_id)
 Closes the specified attribute.
 
hid_t H5Acreate2 (hid_t loc_id, const char *attr_name, hid_t type_id, hid_t space_id, hid_t acpl_id, hid_t aapl_id)
 Creates an attribute attached to a specified object.
 
hid_t H5Acreate_by_name (hid_t loc_id, const char *obj_name, const char *attr_name, hid_t type_id, hid_t space_id, hid_t acpl_id, hid_t aapl_id, hid_t lapl_id)
 Creates an attribute attached to a specified object.
 
herr_t H5Adelete (hid_t loc_id, const char *attr_name)
 Deletes an attribute from a specified location.
 
herr_t H5Adelete_by_idx (hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, hid_t lapl_id)
 Deletes an attribute from an object according to index order.
 
herr_t H5Adelete_by_name (hid_t loc_id, const char *obj_name, const char *attr_name, hid_t lapl_id)
 Removes an attribute from a specified location.
 
htri_t H5Aexists (hid_t obj_id, const char *attr_name)
 Determines whether an attribute with a given name exists on an object.
 
htri_t H5Aexists_by_name (hid_t obj_id, const char *obj_name, const char *attr_name, hid_t lapl_id)
 Determines whether an attribute with a given name exists on an object.
 
hid_t H5Aget_create_plist (hid_t attr_id)
 Gets an attribute creation property list identifier.
 
herr_t H5Aget_info (hid_t attr_id, H5A_info_t *ainfo)
 Retrieves attribute information by attribute identifier.
 
herr_t H5Aget_info_by_idx (hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, H5A_info_t *ainfo, hid_t lapl_id)
 Retrieves attribute information by attribute index position.
 
herr_t H5Aget_info_by_name (hid_t loc_id, const char *obj_name, const char *attr_name, H5A_info_t *ainfo, hid_t lapl_id)
 Retrieves attribute information by attribute name.
 
ssize_t H5Aget_name (hid_t attr_id, size_t buf_size, char *buf)
 Gets an attribute name.
 
ssize_t H5Aget_name_by_idx (hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, char *name, size_t size, hid_t lapl_id)
 Gets an attribute name by attribute index position.
 
hid_t H5Aget_space (hid_t attr_id)
 Gets a copy of the dataspace for an attribute.
 
hsize_t H5Aget_storage_size (hid_t attr_id)
 Returns the amount of storage used to store an attribute.
 
hid_t H5Aget_type (hid_t attr_id)
 Gets an attribute's datatype.
 
herr_t H5Aiterate2 (hid_t loc_id, H5_index_t idx_type, H5_iter_order_t order, hsize_t *idx, H5A_operator2_t op, void *op_data)
 Calls a user-defined function for each attribute on an object.
 
herr_t H5Aiterate_by_name (hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t *idx, H5A_operator2_t op, void *op_data, hid_t lapl_id)
 Calls user-defined function for each attribute on an object.
 
hid_t H5Aopen (hid_t obj_id, const char *attr_name, hid_t aapl_id)
 Opens an attribute for an object specified by object identifier and attribute name.
 
hid_t H5Aopen_by_idx (hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, hid_t aapl_id, hid_t lapl_id)
 Opens the nth attribute attached to an object.
 
hid_t H5Aopen_by_name (hid_t loc_id, const char *obj_name, const char *attr_name, hid_t aapl_id, hid_t lapl_id)
 Opens an attribute for an object by object name and attribute name.
 
herr_t H5Aread (hid_t attr_id, hid_t type_id, void *buf)
 Reads the value of an attribute.
 
herr_t H5Arename (hid_t loc_id, const char *old_name, const char *new_name)
 Renames an attribute.
 
herr_t H5Awrite (hid_t attr_id, hid_t type_id, const void *buf)
 Writes data to an attribute.
 
herr_t H5Arename_by_name (hid_t loc_id, const char *obj_name, const char *old_attr_name, const char *new_attr_name, hid_t lapl_id)
 
hid_t H5Acreate1 (hid_t loc_id, const char *name, hid_t type_id, hid_t space_id, hid_t acpl_id)
 Creates an attribute attached to a specified object.
 
int H5Aget_num_attrs (hid_t loc_id)
 Determines the number of attributes attached to an object.
 
herr_t H5Aiterate1 (hid_t loc_id, unsigned *idx, H5A_operator1_t op, void *op_data)
 Calls a user's function for each attribute on an object.
 
hid_t H5Aopen_idx (hid_t loc_id, unsigned idx)
 Opens the attribute specified by its index.
 
hid_t H5Aopen_name (hid_t loc_id, const char *name)
 Opens an attribute specified by name.
 

Macro Definition Documentation

◆ H5Acreate

#define H5Acreate   H5Acreate2

H5Acreate() is a macro that is mapped to either H5Acreate1() or H5Acreate2().

See also
API Compatibility Macros

◆ H5Aiterate

#define H5Aiterate   H5Aiterate2

H5Aiterate() is a macro that is mapped to either H5Aiterate1() or H5Aiterate2().

See also
API Compatibility Macros

Function Documentation

◆ H5Aclose()

herr_t H5Aclose ( hid_t  attr_id)

Closes the specified attribute.

Parameters
[in]attr_idAttribute identifier
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Aclose() terminates access to the attribute through attr_id and releases the identifier.

Example
{
__label__ fail_acpl, fail_attr, fail_file;
hid_t file, acpl, fspace, attr;
unsigned mode = H5F_ACC_TRUNC;
char file_name[] = "f1.h5";
// attribute names can be arbitrary Unicode strings
char attr_name[] = "Χαρακτηριστικό";
if ((file = H5Fcreate(file_name, mode, H5P_DEFAULT, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_file;
}
ret_val = EXIT_FAILURE;
goto fail_acpl;
}
// use UTF-8 encoding for the attribute name
ret_val = EXIT_FAILURE;
goto fail_fspace;
}
// create a scalar (singleton) attribute
if ((fspace = H5Screate(H5S_SCALAR)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_fspace;
}
// create an attribute on the root group
if ((attr = H5Acreate2(file, attr_name, H5T_STD_I32LE, fspace, acpl, H5P_DEFAULT)) ==
ret_val = EXIT_FAILURE;
goto fail_attr;
}
H5Aclose(attr);
fail_attr:
H5Sclose(fspace);
fail_fspace:
H5Pclose(acpl);
fail_acpl:
H5Fclose(file);
fail_file:;
}
#define H5F_ACC_TRUNC
Definition H5Fpublic.h:50
int64_t hid_t
Definition H5Ipublic.h:60
#define H5I_INVALID_HID
Definition H5Ipublic.h:75
#define H5P_ATTRIBUTE_CREATE
Definition H5Ppublic.h:112
#define H5P_DEFAULT
Definition H5Ppublic.h:228
@ H5S_SCALAR
Definition H5Spublic.h:77
@ H5T_CSET_UTF8
Definition H5Tpublic.h:96
herr_t H5Pset_char_encoding(hid_t plist_id, H5T_cset_t encoding)
Sets the character encoding used to encode link and attribute names.
hid_t H5Acreate2(hid_t loc_id, const char *attr_name, hid_t type_id, hid_t space_id, hid_t acpl_id, hid_t aapl_id)
Creates an attribute attached to a specified object.
herr_t H5Aclose(hid_t attr_id)
Closes the specified attribute.
herr_t H5Fclose(hid_t file_id)
Terminates access to an HDF5 file.
hid_t H5Fcreate(const char *filename, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
Creates an HDF5 file.
herr_t H5Sclose(hid_t space_id)
Releases and terminates access to a dataspace.
hid_t H5Screate(H5S_class_t type)
Creates a new dataspace of a specified type.
#define H5T_STD_I32LE
Definition H5Tpublic.h:323
herr_t H5Pclose(hid_t plist_id)
Terminates access to a property list.
hid_t H5Pcreate(hid_t cls_id)
Creates a new property list as an instance of a property list class.
Since
1.0.0
See also
H5Acreate(), H5Aopen()

◆ H5Acreate1()

hid_t H5Acreate1 ( hid_t  loc_id,
const char *  name,
hid_t  type_id,
hid_t  space_id,
hid_t  acpl_id 
)

Creates an attribute attached to a specified object.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]nameName of attribute to locate and open
[in]type_idIdentifier of attribute datatype
[in]space_idDataspace identifier
[in]acpl_idAttribute creation property list identifier
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.
Deprecated:
Superseded by H5Acreate2().
Note
The acpl parameter is currently not used; specify H5P_DEFAULT.

H5Acreate1() creates an attribute, name, which is attached to the object specified by the identifier loc_id.

The attribute name, name, must be unique for the object.

The attribute is created with the specified datatype and dataspace, type_id and space_id.

Since
1.8.0
Version
1.8.0 The function H5Acreate() was renamed to H5Acreate1() and deprecated in this release.
See also
H5Aclose()

◆ H5Acreate2()

hid_t H5Acreate2 ( hid_t  loc_id,
const char *  attr_name,
hid_t  type_id,
hid_t  space_id,
hid_t  acpl_id,
hid_t  aapl_id 
)

Creates an attribute attached to a specified object.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]attr_nameName of attribute
[in]type_idAttribute datatype identifier
[in]space_idDataspace identifier
[in]acpl_idAttribute creation property list identifier
[in]aapl_idAttribute access property list identifier
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.

H5Acreate2() creates an attribute, attr_name, which is attached to the object specified by the identifier loc_id.

The attribute name, attr_name, must be unique for the object.

The attribute is created with the specified datatype and dataspace, type_id and space_id.

Note
The aapl_id parameter is currently not used; specify H5P_DEFAULT.

The attribute identifier returned by this function must be released with H5Aclose() or resource leaks will develop.

Note
If loc_id is a file identifier, the attribute will be attached to that file's root group.
Example
{
__label__ fail_acpl, fail_attr, fail_file;
hid_t file, acpl, fspace, attr;
unsigned mode = H5F_ACC_TRUNC;
char file_name[] = "f1.h5";
// attribute names can be arbitrary Unicode strings
char attr_name[] = "Χαρακτηριστικό";
if ((file = H5Fcreate(file_name, mode, H5P_DEFAULT, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_file;
}
ret_val = EXIT_FAILURE;
goto fail_acpl;
}
// use UTF-8 encoding for the attribute name
ret_val = EXIT_FAILURE;
goto fail_fspace;
}
// create a scalar (singleton) attribute
if ((fspace = H5Screate(H5S_SCALAR)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_fspace;
}
// create an attribute on the root group
if ((attr = H5Acreate2(file, attr_name, H5T_STD_I32LE, fspace, acpl, H5P_DEFAULT)) ==
ret_val = EXIT_FAILURE;
goto fail_attr;
}
H5Aclose(attr);
fail_attr:
H5Sclose(fspace);
fail_fspace:
H5Pclose(acpl);
fail_acpl:
H5Fclose(file);
fail_file:;
}
Since
1.8.0
See also
H5Aclose()

◆ H5Acreate_by_name()

hid_t H5Acreate_by_name ( hid_t  loc_id,
const char *  obj_name,
const char *  attr_name,
hid_t  type_id,
hid_t  space_id,
hid_t  acpl_id,
hid_t  aapl_id,
hid_t  lapl_id 
)

Creates an attribute attached to a specified object.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName, relative to loc_id, of object that attribute is to be attached to
[in]attr_nameAttribute name
[in]type_idAttribute datatype identifier
[in]space_idDataspace identifier
[in]acpl_idAttribute creation property list identifier
[in]aapl_idAttribute access property list identifier
[in]lapl_idLink access property list identifier
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.

H5Acreate_by_name() creates an attribute, attr_name, which is attached to the object specified by loc_id and obj_name.

loc_id is a location identifier; obj_name is the object name relative to loc_id.

The attribute name, attr_name, must be unique for the object.

The attribute is created with the specified datatype and dataspace, type_id and space_id.

Note
The aapl_id parameter is currently not used; specify H5P_DEFAULT.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Adelete()

herr_t H5Adelete ( hid_t  loc_id,
const char *  attr_name 
)

Deletes an attribute from a specified location.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]attr_nameName of the attribute to delete
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Adelete() removes the attribute specified by its name, attr_name, from a file, dataset, group, or named datatype.

Attention
This function should not be used when other attribute identifiers are open on loc_id. This may cause the internal indexes of the attributes to change and future writes to the open attributes to produce incorrect results.
Example
{
__label__ fail_attr, fail_file;
hid_t file;
unsigned mode = H5F_ACC_RDWR;
char file_name[] = "f1.h5";
char attr_name[] = "Χαρακτηριστικό";
if ((file = H5Fopen(file_name, mode, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_file;
}
// delete the attribute
if (H5Adelete(file, attr_name) < 0) {
ret_val = EXIT_FAILURE;
goto fail_attr;
}
fail_attr:
H5Fclose(file);
fail_file:;
}
#define H5F_ACC_RDWR
Definition H5Fpublic.h:49
herr_t H5Adelete(hid_t loc_id, const char *attr_name)
Deletes an attribute from a specified location.
hid_t H5Fopen(const char *filename, unsigned flags, hid_t fapl_id)
Opens an existing HDF5 file.
Since
1.0.0

◆ H5Adelete_by_idx()

herr_t H5Adelete_by_idx ( hid_t  loc_id,
const char *  obj_name,
H5_index_t  idx_type,
H5_iter_order_t  order,
hsize_t  n,
hid_t  lapl_id 
)

Deletes an attribute from an object according to index order.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object, relative to location, from which attribute is to be removed
[in]idx_typeType of index
[in]orderOrder in which to iterate over the index
[in]nOffset within the index
[in]lapl_idLink access property list identifier
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Adelete_by_idx() removes an attribute specified by its location in an index, from an object.

The object from which the attribute is to be removed is specified by a location identifier and name, loc_id and obj_name, respectively.

The attribute to be removed is specified by a position in an index, n. The type of index is specified by idx_type. The order in which the index is to be traversed is specified by order. For example, if idx_type, order, and n are set to H5_INDEX_NAME, H5_ITER_INC, and 5, respectively, the fifth attribute in the lexicographic order of attribute names will be removed.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Adelete_by_name()

herr_t H5Adelete_by_name ( hid_t  loc_id,
const char *  obj_name,
const char *  attr_name,
hid_t  lapl_id 
)

Removes an attribute from a specified location.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object, relative to location, from which attribute is to be removed
[in]attr_nameName of attribute to delete
[in]lapl_idLink access property list identifier
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Adelete_by_name() removes the attribute attr_name from an object specified by location and name, loc_id and obj_name, respectively.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Aexists()

htri_t H5Aexists ( hid_t  obj_id,
const char *  attr_name 
)

Determines whether an attribute with a given name exists on an object.

Parameters
[in]obj_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]attr_nameAttribute name
Returns
Returns zero (false), a positive (true) or a negative (failure) value.

H5Aexists() determines whether the attribute attr_name exists on the object specified by obj_id.

Since
1.8.0

◆ H5Aexists_by_name()

htri_t H5Aexists_by_name ( hid_t  obj_id,
const char *  obj_name,
const char *  attr_name,
hid_t  lapl_id 
)

Determines whether an attribute with a given name exists on an object.

Parameters
[in]obj_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameObject name
[in]attr_nameAttribute name
[in]lapl_idLink access property list identifier
Returns
Returns zero (false), a positive (true) or a negative (failure) value.

H5Aexists_by_name() determines whether the attribute attr_name exists on an object. That object is specified by its location and name, loc_id and obj_name, respectively.

loc_id specifies a location in the file containing the object. obj_name is the name of the object to which the attribute is attached and can be a relative name, relative to loc_id, or an absolute name, based on the root group of the file.

The link access property list, lapl_id, may provide information regarding the properties of links required to access obj_name.

Since
1.8.0

◆ H5Aget_create_plist()

hid_t H5Aget_create_plist ( hid_t  attr_id)

Gets an attribute creation property list identifier.

Parameters
[in]attr_idAttribute identifier
Returns
Returns an attribute's creation property list identifier if successful; otherwise returns H5I_INVALID_HID.

H5Aget_create_plist() returns an identifier for the attribute creation property list associated with the attribute specified by attr_id.

The creation property list identifier should be released with H5Pclose() to prevent resource leaks.

Since
1.8.0

◆ H5Aget_info()

herr_t H5Aget_info ( hid_t  attr_id,
H5A_info_t ainfo 
)

Retrieves attribute information by attribute identifier.

Parameters
[in]attr_idAttribute identifier
[out]ainfoAttribute information struct
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Aget_info() retrieves attribute information, locating the attribute with an attribute identifier, attr_id. The attribute information is returned in the ainfo struct.

Since
1.8.0

◆ H5Aget_info_by_idx()

herr_t H5Aget_info_by_idx ( hid_t  loc_id,
const char *  obj_name,
H5_index_t  idx_type,
H5_iter_order_t  order,
hsize_t  n,
H5A_info_t ainfo,
hid_t  lapl_id 
)

Retrieves attribute information by attribute index position.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object to which attribute is attached, relative to location
[in]idx_typeType of index
[in]orderIndex traversal order
[in]nAttribute's position in index
[out]ainfoStruct containing returned attribute information
[in]lapl_idLink access property list identifier
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Aget_info_by_idx() retrieves information for an attribute that is attached to an object, which is specified by its location and name, loc_id and obj_name, respectively. The attribute is located by its index position, and the attribute information is returned in the ainfo struct.

The attribute is located by means of an index type, an index traversal order, and a position in the index, idx_type, order and n, respectively.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Aget_info_by_name()

herr_t H5Aget_info_by_name ( hid_t  loc_id,
const char *  obj_name,
const char *  attr_name,
H5A_info_t ainfo,
hid_t  lapl_id 
)

Retrieves attribute information by attribute name.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of the object to which an attribute is attached, relative to location
[in]attr_nameAttribute name
[out]ainfoStruct containing returned attribute information
[in]lapl_idLink access property list identifier
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Aget_info_by_name() retrieves information for an attribute, attr_name, that is attached to an object specified by its location and name, loc_id and obj_name, respectively. The attribute information is returned in the ainfo struct.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Aget_name()

ssize_t H5Aget_name ( hid_t  attr_id,
size_t  buf_size,
char *  buf 
)

Gets an attribute name.

Parameters
[in]attr_idAttribute identifier
[in]buf_sizeThe size of the buffer to store the name in
[out]bufBuffer to store name in
Returns
Returns the length of the attribute's name, which may be longer than buf_size, if successful. Otherwise, returns a negative value.

H5Aget_name() retrieves the name of an attribute specified by the identifier, attr_id.

Up to size characters of the attribute name are returned in name; additional characters, if any, are not returned to the user application.

If the length of the attribute name, which determines the required value of size, is unknown, a preliminary call to H5Aget_name() with the last two parameters set to NULL and zero respectively can be made. The return value of this call will be the size in bytes of the attribute name. That value, plus 1 for a NULL terminator, must then be assigned to size for a second H5Aget_name() call, which will retrieve the actual attribute name.

Since
1.0.0

◆ H5Aget_name_by_idx()

ssize_t H5Aget_name_by_idx ( hid_t  loc_id,
const char *  obj_name,
H5_index_t  idx_type,
H5_iter_order_t  order,
hsize_t  n,
char *  name,
size_t  size,
hid_t  lapl_id 
)

Gets an attribute name by attribute index position.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object to which attribute is attached, relative to location
[in]idx_typeType of index
[in]orderIndex traversal order
[in]nAttribute's position in index
[out]nameAttribute name
[in]sizeSize, in bytes, of attribute name
[in]lapl_idLink access property list identifier
Returns
Returns attribute name size, in bytes, if successful; otherwise, returns a negative value.

H5Aget_name_by_idx() retrieves the name of an attribute that is attached to an object, which is specified by its location and name, loc_id and obj_name, respectively. The attribute is located by its index position, the size of the name is specified in size, and the attribute name is returned in name.

The attribute is located by means of an index type, an index traversal order, and a position in the index, idx_type, order and n, respectively.

Up to size characters of the attribute name are returned in name; additional characters, if any, are not returned to the user application.

If the length of the attribute name, which determines the required value of size, is unknown, a preliminary call to H5Aget_name_by_idx() with the last two parameters set to NULL and zero respectively can be made. The return value of this call will be the size in bytes of the attribute name. That value, plus 1 for a NULL terminator, must then be assigned to size for a second H5Aget_name_by_idx() call, which will retrieve the actual attribute name.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Aget_num_attrs()

int H5Aget_num_attrs ( hid_t  loc_id)

Determines the number of attributes attached to an object.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
Returns
Returns the number of attributes if successful; otherwise, returns a negative value.
Deprecated:
Superseded by H5Oget_info(), H5Oget_info_by_name(), and H5Oget_info_by_idx().

H5Aget_num_attrs() returns the number of attributes attached to the object specified by its identifier, loc_id.

Since
1.0.0

◆ H5Aget_space()

hid_t H5Aget_space ( hid_t  attr_id)

Gets a copy of the dataspace for an attribute.

Parameters
[in]attr_idAttribute identifier
Returns
Returns an attribute dataspace identifier if successful; otherwise returns H5I_INVALID_HID.

H5Aget_space() retrieves a copy of the dataspace for an attribute. The dataspace identifier returned from this function must be released with H5Sclose() or resource leaks will develop.

Since
1.0.0

◆ H5Aget_storage_size()

hsize_t H5Aget_storage_size ( hid_t  attr_id)

Returns the amount of storage used to store an attribute.

Parameters
[in]attr_idAttribute identifier
Returns
Returns the amount of storage size allocated for the attribute; otherwise, returns 0 (zero).

H5Aget_storage_size() returns the amount of storage that is required for the specified attribute, attr_id.

Since
1.6.0

◆ H5Aget_type()

hid_t H5Aget_type ( hid_t  attr_id)

Gets an attribute's datatype.

Parameters
[in]attr_idAttribute identifier
Returns
Returns a datatype identifier if successful; otherwise returns H5I_INVALID_HID.

H5Aget_type() retrieves a copy of the attribute's datatype. The datatype is reopened if it is a named type before returning it to the application. The datatypes returned by this function are always read-only.

The datatype identifier returned from this function must be released with H5Tclose() or resource leaks will develop.

Since
1.0.0

◆ H5Aiterate1()

herr_t H5Aiterate1 ( hid_t  loc_id,
unsigned *  idx,
H5A_operator1_t  op,
void *  op_data 
)

Calls a user's function for each attribute on an object.

Parameters
[in]loc_idLocation identifier
[in,out]idxStarting (in) and ending (out) attribute index
[in]opUser's function to pass each attribute to
[in,out]op_dataUser's data to pass through to the iterator operator function
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.
Deprecated:
Superseded by H5Aiterate2().

H5Aiterate1() iterates over the attributes of the object specified by its identifier, loc_id. The object can be a group, dataset, or named datatype. For each attribute of the object, the op_data and some additional information specified below are passed to the operator function op. The iteration begins with the attribute specified by its index, idx; the index for the next attribute to be processed by the operator, op, is returned in idx. If idx is the null pointer, then all attributes are processed.

Warning
Adding or removing attributes to the object during iteration will lead to undefined behavior.
Version
1.8.0 The function H5Aiterate was renamed to H5Aiterate1() and deprecated in this release.
Since
1.0.0

◆ H5Aiterate2()

herr_t H5Aiterate2 ( hid_t  loc_id,
H5_index_t  idx_type,
H5_iter_order_t  order,
hsize_t idx,
H5A_operator2_t  op,
void *  op_data 
)

Calls a user-defined function for each attribute on an object.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]idx_typeType of index
[in]orderOrder in which to iterate over index
[in,out]idxInitial and returned offset within index
[in]opUser-defined function to pass each attribute to
[in,out]op_dataUser data to pass through to and to be returned by iterator operator function
Returns
Returns a non-negative value if successful; otherwise, returns a negative value. Further note that this function returns the return value of the last operator if it was non-zero, which can be a negative value, zero if all attributes were processed, or a positive value indicating short-circuit success.

H5Aiterate2() iterates over the attributes attached to a dataset, named datatype, or group, as specified by loc_id. For each attribute, user-provided data, op_data, with additional information, as defined below, is passed to a user-defined function, op, which operates on that attribute.

The order of the iteration and the attributes iterated over are specified by three parameters: the index type, idx_type; the order in which the index is to be traversed, order; and the attribute's position in the index, idx. The next attribute to be operated on is specified by idx, a position in the index.

For example, if idx_type, order, and idx are set to H5_INDEX_NAME, H5_ITER_INC, and 5, respectively, the attribute in question is the fifth attribute from the beginning of the alphanumeric index of attribute names. If order were set to H5_ITER_DEC, it would be the fifth attribute from the end of the index.

The parameter idx is passed in on an H5Aiterate2() call with one value and may be returned with another value. The value passed in identifies the parameter to be operated on first; the value returned identifies the parameter to be operated on in the next step of the iteration.

Note
This function is also available through the H5Aiterate() macro.
Warning
Adding or removing attributes to the object during iteration will lead to undefined behavior.
Since
1.8.0

◆ H5Aiterate_by_name()

herr_t H5Aiterate_by_name ( hid_t  loc_id,
const char *  obj_name,
H5_index_t  idx_type,
H5_iter_order_t  order,
hsize_t idx,
H5A_operator2_t  op,
void *  op_data,
hid_t  lapl_id 
)

Calls user-defined function for each attribute on an object.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object, relative to location
[in]idx_typeType of index
[in]orderOrder in which to iterate over index
[in,out]idxInitial and returned offset within index
[in]opUser-defined function to pass each attribute to
[in,out]op_dataUser data to pass through to and to be returned by iterator operator function
[in]lapl_idLink access property list identifier
Returns
Returns a non-negative value if successful; otherwise, returns a negative value. Further note that this function returns the return value of the last operator if it is non-zero, which can be a negative value, zero if all attributes were processed, or a positive value indicating short-circuit success.

H5Aiterate_by_name() iterates over the attributes attached to the dataset or group specified with loc_id and obj_name. For each attribute, user-provided data, op_data, with additional information, as defined below, is passed to a user-defined function, op, which operates on that attribute.

The order of the iteration and the attributes iterated over are specified by three parameters: the index type, idx_type; the order in which the index is to be traversed, order; and the attribute's position in the index, idx. The next attribute to be operated on is specified by idx, a position in the index.

For example, if idx_type, order, and idx are set to H5_INDEX_NAME, H5_ITER_INC, and 5, respectively, the attribute in question is the fifth attribute from the beginning of the alphanumeric index of attribute names. If order were set to H5_ITER_DEC, it would be the fifth attribute from the end of the index.

The parameter idx is passed in on an H5Aiterate_by_name() call with one value and may be returned with another value. The value passed in identifies the parameter to be operated on first; the value returned identifies the parameter to be operated on in the next step of the iteration.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Warning
Adding or removing attributes to the object during iteration will lead to undefined behavior.
Since
1.8.0

◆ H5Aopen()

hid_t H5Aopen ( hid_t  obj_id,
const char *  attr_name,
hid_t  aapl_id 
)

Opens an attribute for an object specified by object identifier and attribute name.

Parameters
[in]obj_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]attr_nameName of attribute to open
[in]aapl_idAttribute access property list identifier
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.

H5Aopen() opens an existing attribute, attr_name, that is attached to the object specified by an object identifier, obj_id.

Note
The aapl_id parameter is currently not used; specify H5P_DEFAULT.

This function, H5Aopen_by_idx() or H5Aopen_by_name() must be called before the attribute can be accessed for any further purpose, including reading, writing, or any modification.

The attribute identifier returned by this function must be released with H5Aclose() or resource leaks will develop.

Example
{
__label__ fail_attr, fail_file;
hid_t file, attr;
unsigned mode = H5F_ACC_RDONLY;
char file_name[] = "f1.h5";
char attr_name[] = "Χαρακτηριστικό";
int value;
if ((file = H5Fopen(file_name, mode, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_file;
}
if ((attr = H5Aopen(file, attr_name, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_attr;
}
// read the attribute value
if (H5Aread(attr, H5T_NATIVE_INT, &value) < 0)
ret_val = EXIT_FAILURE;
// do something w/ the attribute value
H5Aclose(attr);
fail_attr:
H5Fclose(file);
fail_file:;
}
#define H5F_ACC_RDONLY
Definition H5Fpublic.h:48
hid_t H5Aopen(hid_t obj_id, const char *attr_name, hid_t aapl_id)
Opens an attribute for an object specified by object identifier and attribute name.
herr_t H5Aread(hid_t attr_id, hid_t type_id, void *buf)
Reads the value of an attribute.
#define H5T_NATIVE_INT
Definition H5Tpublic.h:780
Since
1.8.0
See also
H5Aclose(), H5Acreate()

◆ H5Aopen_by_idx()

hid_t H5Aopen_by_idx ( hid_t  loc_id,
const char *  obj_name,
H5_index_t  idx_type,
H5_iter_order_t  order,
hsize_t  n,
hid_t  aapl_id,
hid_t  lapl_id 
)

Opens the nth attribute attached to an object.

Parameters
[in]loc_idLocation identifier
[in]obj_nameName of object to which attribute is attached, relative to location
[in]idx_typeType of index
[in]orderIndex traversal order
[in]nAttribute's position in index
[in]aapl_idAttribute access property list identifier
[in]lapl_idLink access property list identifier
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.

H5Aopen_by_idx() opens an existing attribute that is attached to an object specified by location and name, loc_id and obj_name, respectively.

The attribute is identified by an index type, an index traversal order, and a position in the index, idx_type, order and n, respectively.

Note
The aapl_id parameter is currently not used; specify H5P_DEFAULT.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

This function, H5Aopen(), or H5Aopen_by_name() must be called before an attribute can be accessed for any further purpose, including reading, writing, or any modification.

The attribute identifier returned by this function must be released with H5Aclose() or resource leaks will develop.

Since
1.8.0

◆ H5Aopen_by_name()

hid_t H5Aopen_by_name ( hid_t  loc_id,
const char *  obj_name,
const char *  attr_name,
hid_t  aapl_id,
hid_t  lapl_id 
)

Opens an attribute for an object by object name and attribute name.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object to which attribute is attached, relative to loc_id
[in]attr_nameName of attribute to open
[in]aapl_idAttribute access property list identifier
[in]lapl_idLink access property list identifier
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.

H5Aopen_by_name() opens an existing attribute, attr_name, that is attached to an object specified by location and name, loc_id and obj_name, respectively.

loc_id specifies a location from which the target object can be located and obj_name is an object name relative to loc_id.

Note
The aapl_id parameter is currently not used; specify H5P_DEFAULT.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

This function, H5Aopen(), or H5Aopen_by_idx() must be called before an attribute can be accessed for any further purpose, including reading, writing, or any modification.

The attribute identifier returned by this function must be released with H5Aclose() or resource leaks will develop.

Since
1.8.0

◆ H5Aopen_idx()

hid_t H5Aopen_idx ( hid_t  loc_id,
unsigned  idx 
)

Opens the attribute specified by its index.

Parameters
[in]loc_idLocation identifier
[in]idxIndex of the attribute to open
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.
Deprecated:
Superseded by H5Aopen_by_idx().

H5Aopen_idx() opens an attribute that is attached to the object specified with loc_id. The location object may be either a group, dataset, or named datatype, all of which may have any sort of attribute. The attribute specified by the index, idx, indicates the attribute to access. The value of idx is a 0-based, non-negative integer. The attribute identifier returned from this function must be released with H5Aclose() or resource leaks will develop.

Since
1.0.0

◆ H5Aopen_name()

hid_t H5Aopen_name ( hid_t  loc_id,
const char *  name 
)

Opens an attribute specified by name.

Parameters
[in]loc_idLocation identifier
[in]nameAttribute name
Returns
Returns an attribute identifier if successful; otherwise returns H5I_INVALID_HID.
Deprecated:
Superseded by H5Aopen_by_name().

H5Aopen_name() opens an attribute specified by its name, name, which is attached to the object specified with loc_id. The location object may be either a group, dataset, or named datatype, which may have any sort of attribute. The attribute identifier returned from this function must be released with H5Aclose() or resource leaks will develop.

Since
1.0.0

◆ H5Aread()

herr_t H5Aread ( hid_t  attr_id,
hid_t  type_id,
void *  buf 
)

Reads the value of an attribute.

Parameters
[in]attr_idAttribute identifier
[in]type_idDatatype (in-memory) identifier
[out]bufBuffer for data to be read
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Aread() reads an attribute, specified with attr_id. The attribute's in-memory datatype is specified with type_id. The entire attribute is read into buf from the file.

Datatype conversion takes place at the time of a read or write and is automatic.

Example
{
__label__ fail_attr, fail_file;
hid_t file, attr;
unsigned mode = H5F_ACC_RDONLY;
char file_name[] = "f1.h5";
char attr_name[] = "Χαρακτηριστικό";
int value;
if ((file = H5Fopen(file_name, mode, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_file;
}
if ((attr = H5Aopen(file, attr_name, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_attr;
}
// read the attribute value
if (H5Aread(attr, H5T_NATIVE_INT, &value) < 0)
ret_val = EXIT_FAILURE;
// do something w/ the attribute value
H5Aclose(attr);
fail_attr:
H5Fclose(file);
fail_file:;
}
Version
1.8.8 Fortran updated to Fortran2003.
1.4.2 The dims parameter was added to the Fortran API in this release.
Since
1.0.0
See also
H5Awrite()

◆ H5Arename()

herr_t H5Arename ( hid_t  loc_id,
const char *  old_name,
const char *  new_name 
)

Renames an attribute.

Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]old_nameName of the attribute to be changed
[in]new_nameNew name for the attribute
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Arename() changes the name of the attribute located at loc_id.

The old name, old_name, is changed to the new name, new_name.

Since
1.6.0

◆ H5Arename_by_name()

herr_t H5Arename_by_name ( hid_t  loc_id,
const char *  obj_name,
const char *  old_attr_name,
const char *  new_attr_name,
hid_t  lapl_id 
)
Parameters
[in]loc_idLocation identifier. The identifier may be that of a file, group, dataset, or named datatype.
[in]obj_nameName of object, relative to location, whose attribute is to be renamed
[in]old_attr_namePrior attribute name
[in]new_attr_nameNew attribute name
[in]lapl_idLink access property list identifier

H5Arename_by_name() changes the name of attribute that is attached to the object specified by loc_id and obj_name. The attribute named old_attr_name is renamed new_attr_name.

The link access property list, lapl_id, may provide information regarding the properties of links required to access the object, obj_name.

Since
1.8.0

◆ H5Awrite()

herr_t H5Awrite ( hid_t  attr_id,
hid_t  type_id,
const void *  buf 
)

Writes data to an attribute.

Parameters
[in]attr_idAttribute identifier
[in]type_idDatatype (in-memory) identifier
[out]bufData to be written
Returns
Returns a non-negative value if successful; otherwise, returns a negative value.

H5Awrite() writes an attribute, specified with attr_id. The attribute's in-memory datatype is specified with type_id. The entire attribute is written from buf to the file.

Datatype conversion takes place at the time of a read or write and is automatic.

Example
{
__label__ fail_attr, fail_file;
hid_t file, attr;
unsigned mode = H5F_ACC_RDWR;
char file_name[] = "f1.h5";
char attr_name[] = "Χαρακτηριστικό";
int value = 1234;
if ((file = H5Fopen(file_name, mode, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_file;
}
if ((attr = H5Aopen(file, attr_name, H5P_DEFAULT)) == H5I_INVALID_HID) {
ret_val = EXIT_FAILURE;
goto fail_attr;
}
// update the attribute value
if (H5Awrite(attr, H5T_NATIVE_INT, &value) < 0)
ret_val = EXIT_FAILURE;
H5Aclose(attr);
fail_attr:
H5Fclose(file);
fail_file:;
}
herr_t H5Awrite(hid_t attr_id, hid_t type_id, const void *buf)
Writes data to an attribute.
Version
1.8.8 Fortran updated to Fortran2003.
1.4.2 Fortran dims parameter added in this release
Since
1.0.0
See also
H5Aread()