
  extract

  extract (grep/select) line parameters from spectroscopic data base file

  usage:
  extract  [options]  line_parameter_database

  command line options:
    -h            help 
   --help         help extended
    -c   char(s)  comment character used in output file (default #)
    -o   file     output file (default: standard output, see last note of extended help)
    
    -d   string   output directory (default: save file(s) in current directory)
    -f   string   output format:  original or simple lists (position vs strengths etc)
                                  default "vSEan" (see notes of extended help)
    -i   integer  isotope name (e.g. 4 or 162 for heavy water HDO, the fourth most abundant isotope)
    -m   string   molecule name  (one molecule only!)
    -S   float    minimum line strength to accept
    -x   interval lower and upper end of spectral (default: wavenumber) range (comma separated pair without blanks)
    -X   string   unit used for setting spectral range with -x option (does not affect output listing!)
                  (default: "cm-1",  other choices: "Hz", "MHz", "GHz", "mue", "nm")

  

  OUTPUT FORMAT:
    *  "simple lists" --- for each molecule a (tabular ascii) file with columns for position etc is generated
                          (where the filename is set automatically by molecule name with the format indicated by the extension)

       The actual format is defined by a combination of single letters
       "v" --- wavenumber/frequency position   (Hint: the letter "v" looks like the greek nu)
       "S" --- Strengths
       "E" --- Energy (lower state)
       "a" --- air broadening half width (pressure, collision broadening)
       "s" --- self broadening half width
       "n" --- temperature exponent n of pressure broadening
       "i" --- isotope number
       "b" --- broadening parameters, equivalent to "asni"
       
       use "vSEan" or "vSEasni"="vSEb" to produce a line list acceptable by lbl2xs and lbl2od
       use "o" or "h" or "g" to save the extract in the original format

       Valid formats are:   "o", "g", "h",  "vS","vSE","vSEa","vSEb","vSEan","vSEasn","vSEasni"


  NOTES:
    *  at least wavenumber range OR molecule has to be selected!
    *  molecule names are case sensitive!
    *  extracting lines of some selected molecules simultaneously is (currently) not supported:
       either specify one molecule or none
    *  the database filename must include either the string "hit" or "geisa" or "sao" (case insensitive)
       in order to give extract a chance to read with the proper format!
    *  currently only HITRAN, GEISA or SAO are supported
    *  format conversion hitran <---> geisa not yet implemented
    *  if lines for all gases in a spectral range are to be selected and if the output is to be written
       to a simple line list (format 'vS' etc), separate files are produced for each molecule individually
       (an output file specified with the -o option then lists ALL selected lines in the original format)


