:orphan:
# PetscViewerHDF5ReadAttribute
Read an attribute 
## Synopsis
```
#include "petscviewerhdf5.h" 
PetscErrorCode PetscViewerHDF5ReadAttribute(PetscViewer viewer, const char parent[], const char name[], PetscDataType datatype, const void *defaultValue, void *value)
```
Collective


## Input Parameters

- ***viewer -*** The `PETSCVIEWERHDF5` viewer
- ***parent -*** The parent dataset/group name
- ***name   -*** The attribute name
- ***datatype -*** The attribute type
- ***defaultValue -*** The pointer to the default value



## Output Parameter

- ***value    -*** The pointer to the read HDF5 attribute value





## Notes
If defaultValue is `NULL` and the attribute is not found, an error occurs.

If defaultValue is not `NULL` and the attribute is not found, `defaultValue` is copied to value.

The pointers `defaultValue` and value can be the same; for instance
```none
  flg = PETSC_FALSE;
  PetscCall(`PetscViewerHDF5ReadAttribute`(viewer,name,"attr",PETSC_BOOL,&flg,&flg));
```

is valid, but make sure the default value is initialized.

If the datatype is `PETSC_STRING`, the output string is newly allocated so one must `PetscFree()` it when no longer needed.

If parent starts with '/', it is taken as an absolute path overriding currently pushed group, else parent is relative to the current pushed group. `NULL` means the current pushed group.


## See Also
 [](sec_viewers), `PETSCVIEWERHDF5`, `PetscViewerHDF5Open()`, `PetscViewerHDF5ReadObjectAttribute()`, `PetscViewerHDF5WriteAttribute()`, `PetscViewerHDF5HasAttribute()`, `PetscViewerHDF5HasObject()`, `PetscViewerHDF5PushGroup()`, `PetscViewerHDF5PopGroup()`, `PetscViewerHDF5GetGroup()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/classes/viewer/impls/hdf5/hdf5v.c.html#PetscViewerHDF5ReadAttribute">src/sys/classes/viewer/impls/hdf5/hdf5v.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/classes/viewer/impls/hdf5/hdf5v.c)


[Index of all Viewer routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)