Extract data from CommVault, Netbackup and EMC Data Domain

I want to create a web application where I can extract the data from CommVault, NetBackup and Data Domain Backups and insert them into a thrid backup client such as Rubrik. Is there any way I can do that using a program? Are there API's available for this?
It seems all these providers provide GUI based services and none exposed as code. I did find CommVault SDK which can enable me to browse contents and possibly save data. It would be great help if there could be pointers to others.