extract data from EEG text file

Using the data text file that you provided elsewhere (renamed and attached to this answer), here is a short example of one way to parse it. Note that it is not the best way, but it is good enough for starting the discussion:

buffer = fileread( 'data01.txt' ) ;
pattern = '\[([^\]]+).\s+(\d+)\s+"\s+(\d+)\s+(\d+)\s+(\d)+\s+MCAP-(\S+)\s+(\S+)\s+(\S+)\s+(\S+)' ;
data = regexp( buffer, pattern, 'tokens' ) ;
data = vertcat( data{:} ) ;

Running it outputs a cell array of 830 rows associated with MCAP entries, as follows:

I updated the pattern so REGEXP extracts all other "numeric" columns.

>> data
data =
  830×9 cell array

    {'22:41:37.000 01…'}    {'392192' }    {'0'}    {'0'}    {'0'}    {'A3'}    {'17'}    {'S1'}    {'EEG-F4-C4' }
    {'22:41:57.000 01…'}    {'397312' }    {'0'}    {'0'}    {'0'}    {'A3'}    {'9' }    {'S1'}    {'EEG-F4-C4' }
    {'22:42:13.000 01…'}    {'401408' }    {'0'}    {'0'}    {'0'}    {'A3'}    {'11'}    {'S2'}    {'EEG-F4-C4' }
    {'22:42:28.000 01…'}    {'405248' }    {'0'}    {'0'}    {'0'}    {'A3'}    {'23'}    {'S2'}    {'EEG-F4-C4' }
    ...
    {'07:08:22.000 02…'}    {'8175872'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'8' }    {'S4'}    {'EEG-F4-C4' }
    {'07:11:27.000 02…'}    {'8223232'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'8' }    {'S4'}    {'EEG-Fp2-F4'}
    {'07:12:08.000 02…'}    {'8233728'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'6' }    {'S4'}    {'EEG-Fp2-F4'}
    {'07:18:31.000 02…'}    {'8331776'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'6' }    {'S4'}    {'EEG-F4-C4' }
    {'07:18:53.000 02…'}    {'8337408'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'7' }    {'S4'}    {'EEG-F4-C4' }
    {'07:19:27.000 02…'}    {'8346112'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'15'}    {'S4'}    {'EEG-F4-C4' }
    {'07:20:29.000 02…'}    {'8361984'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'11'}    {'S4'}    {'EEG-F4-C4' }
    {'07:20:48.000 02…'}    {'8366848'}    {'0'}    {'0'}    {'0'}    {'A1'}    {'12'}    {'S4'}    {'EEG-F4-C4' }