USAGE:
           xggp [opt] file

PURPOSE:
           Extracts time and measurement columns from GWR GGP files
           and prints to stdout.
           For the other files there is a sister script
           xchan-units-with-si.pl.
   
OPTIONS:
 -c               - Prints a table of the channels in the file.
                    (by cheating! the print is independent of a file.

 -H c[,c...]      - Prints the header of column c.
                    Each c may be a range c1..c2

 -x c[,c...]      - The requested channel numbers to retrieve
                    Each c may be a range c1..c2

 -m m             - Print only each m'th line
 -n r             - The number of records for output [100000]

EXAMPLE:

  xggp -x 1,3 -n 10 -m 2 MON_o054/GW091000.GGP

retrieves 5 rows (scope 10, every 2'nd) of channels 1 and 3 (gravity and barometer)

Result from example
2009 10 01 00 01 00    -0.95969170   997.17980000
2009 10 01 00 03 00    -0.96379140   997.16170000
2009 10 01 00 05 00    -0.96667990   997.13260000
2009 10 01 00 07 00    -0.97480930   997.09110000
2009 10 01 00 09 00    -0.97712160   997.08270000
...

.bye