# MPI_Attr_get

Retrieves attribute value by key

## Synopsis

    int MPI_Attr_get(MPI_Comm comm, int keyval, void *attribute_val, int *flag)

## Input Parameters

comm
  communicator to which attribute is attached (handle)
keyval
  key value (integer)

## Output Parameters

attribute_val
  attribute value, unless flag = false (None)
flag
  true if an attribute value was extracted; false if no attribute is associated with the key (logical)

## Deprecated Function

The current MPI standard defines this routine as deprecated. The routine may continue to be used, but new code should use the replacement routine. The replacement for this routine is `MPI_Comm_get_attr`.

## Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as `malloc` or other non-MPICH runtime routines that are themselves not interrupt-safe.

## Errors

All MPI routines (except `MPI_Wtime` and `MPI_Wtick`) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with `MPI_Comm_set_errhandler` (for communicators), `MPI_File_set_errhandler` (for files), and `MPI_Win_set_errhandler` (for RMA windows). The MPI-1 routine `MPI_Errhandler_set` may be used but its use is deprecated. The predefined error handler `MPI_ERRORS_RETURN` may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS
  No error; MPI routine completed successfully.

MPI_ERR_OTHER
  Other error; use `MPI_Error_string` to get more information about this error code.

## See Also

MPI_Attr_put, MPI_Keyval_create, MPI_Attr_delete, MPI_Comm_get_attr