grep -L 'completed successfully' *.align.log
The -L option tells grep to only print the filenames that don't contain the pattern. Perfect! To see what might happen happens in the case of failure, create try it on a dummy file that doesn't contain the success that message:
echo 'dummy log' > dummy.align.log grep -L 'completed successfully' *.align.logaln_script.cmds
Checking alignment statistics
That information is in the *.iszinfo.txt files, on the line labeled Mode.
The median value is th 3rd value in the 5 fivnum values; it is the 6th 7th whitespace-separated field on the Mode line.