Go to: Synopsis. Return value. Related. Flags. MEL examples. 
      
       isDirty [-connection] [-datablock] 
string...
      
      isDirty is undoable, NOT queryable, and NOT editable.
      The isDirty command is used to check if a plug is dirty.  The
return value is 0 if it is not and 1 if it is.  If more than one plug
is specified then the result is the logical "or" of all objects
(ie. returns 1 if *any* of the plugs are dirty).
	  
      
      | boolean | Is the plug dirty? If more than one plug is given then it returns the
logical "and" of all dirty states. | 
      
      attributeQuery, getClassification, isConnected, nodeType, objExists, objectType
      
    
      connection, datablock
      
		
		  | Long name (short name) | Argument types | Properties | 
		
	
	  | -datablock(-d) |  |   | 
	
	  | 
	      
		|  | Check the datablock entry for the plug. |  | 
	
	  | -connection(-c) |  |   | 
	
	  | 
	      
		|  | Check the connection of the plug (default). |  | 
      
      
		
		  
			|  Flag can appear in Create mode of command |  Flag can appear in Edit mode of command | 
		  
			|  Flag can appear in Query mode of command |  Flag can be used more than once in a command. | 
		
// Create a plusMinusAverage node and a transform. We use the '-skipSelect'
// flag so that they are not displayed in the Attribute Editor because
// that would force an evaluation and cause the plugs to become clean.
createNode -n pma -skipSelect plusMinusAverage;
createNode -n t -skipSelect transform;
// Hide the transform so that Maya's draw won't force an evaluation which
// would clean its plugs.
hide t;
// Connect the transform's 'tx' to one of the plusMinusAverage node's
// inputs.
connectAttr t.tx pma.input1D[0];
// Set the value of the transform's 'tx' and check that the
// target of the connection has become dirty.
setAttr t.tx 13;
isDirty pma.input1D[0];
// Result: 1 //
// If we retrieve the value of the destination attribute
// then the connection becomes clean.
getAttr pma.input1D[0];
// Result: 13 //
isDirty pma.input1D[0];
// Result: 0 //
// A plusMinusAverage node's 'output1D' attribute depends
// upon the values in its 'input1D' array. Since we haven't
// retrieved its value yet, it should still be dirty. However,
// it seems to be clean:
isDirty pma.output1D;
// Result: 0 //
// The reason for this is that the 'isDirty' command
// by default only checks connections and 'output1D' has
// no connection to be dirty. If we instead check its
// value in the datablock, we get the expected result:
isDirty -d pma.output1D;
// Result: 1 //
// The output value will remain dirty until we
// force its evaluation by retrieving it.
getAttr pma.output1D;
// Result: 13 //
isDirty -d pma.output1D;
// Result: 0 //