[chaley]

I don't think calibredb can do it natively and I don't know how to do it in the windows cmd line. However, a simple python script can convert the output to a comma separated list.

To use it:

• Put this script in some file such as newlines_to_commas.py
  

  import sys
  ans = []
  for line in sys.stdin:
      ans.append(line.strip())
  print(','.join(ans[1:]))

• Run your command storing the output into a file.
  

  calibredb list -f id --with-library "C:\Users\Dirk\Calibre-Bibliothek" --search 'date:<10daysago' > file_with_newlines.txt

• Run the script. If you don't have python installed then use calibre-debug as the python interpreter.
  

  calibre-debug newlines_to_commas.py < file_with_newlines.txt > file_without_newlines.txt

  If you have python installed then use
  

  python newlines_to_commas.py < file_with_newlines.txt > file_without_newlines.txt

• The comma-separated list is now in file_without_newlines.txt