Add line to a bunch of files and run the files

editfiles.py

#!/usr/bin/env python
import pathlib
import subprocess

# Get the list of files we want to modify
p=pathlib.Path('mom6')
filelist=list(p.glob('**/sync_output_to_gdata.sh'))

# Loop on the files
for f in filelist:
  # Add the line
  with f.open('a') as fo:
      # I've added an 'echo' for testing but feel free to remove it
      fo.write('echo rsync --ignore-existing --exclude ".nc." -vrltoD --safe-links restart*0 ${GDATADIR}\n')
  # Make sure file is executable
  f.chmod(0o700)
  
  # Execute script
  subprocess.run(str(f))

thanks @ccarouge