Get the total size of some files:
du -ch /path/patern* | grep total
Get the total number of files being backed up using the log of the RMAN job:
grep -i 'input datafile file number=' rman_BKUP.log | wc -l
Use grep to display the next 2 lines after the pattern you’re looking for (-A= AFTER , B=BEFORE):
grep -i -A 2 'input datafile file number' rman_BKUP.log input datafile file number=00001 name=/storage/datafile.dbf channel ch02: starting piece 1 at 14-MAR-18 15:30:25 channel ch01: finished piece 1 at 14-MAR-18 15:30:32