how to get the recordid in the component which is invoked through quick action present in record page

Okay, then could you please try this : 

<!--parent component invoked from quick action-->
<aura:component implements="flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,force:lightningQuickAction">
    <c:childComponent entityId="{!v.recordId}" />
</aura:component>
<!--child component-->
<aura:component controller="customLookUpController">
    <aura:attribute name="entityId" type="String" access="public" />
    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />
</aura:component>
<!--controller-->
({
    doInit: function(component,event,helper) {
        var getId = component.get( "v.entityId" );
    }
})