nc_dump.m is an m-file that can be used to interrogate the structure of a netCDF file or OPeNDAP dataset. It's about the first command that I use when I need to look at a new dataset.

For this first example, we look at some digital elevation map data on the opendap server at IMCS at Rutgers. Let's take a look at the structure of the data by typing the following commands into your matlab window. Yes, OPeNDAP URLs are ridiculously long... Cut-and-paste is your friend.

>> url = 'http://tashtego.marine.rutgers.edu:8080/thredds/dodsC/other/bathymetry/w100w20s10n90.nc';
>> nc_dump ( url )
netcdf http://tashtego.marine.rutgers.edu:8080/thredds/dodsC/other/bathymetry/w100w20s10n90.nc { 

dimensions:
	lat = 12000 ;
	lon = 9600 ;


variables:
	double lat(lat), shape = [12000]
		lat:long_name = "Latitude" 
		lat:standard_name = "latitude" 
		lat:units = "degrees_north" 
		lat:_FillValue = -999 
		lat:valid_range = -90 90 
		lat:maximum = 89.9958 
		lat:minimum = -9.99583 
		lat:increment = 0.00833333 
	double lon(lon), shape = [9600]
		lon:long_name = "Longitude" 
		lon:standard_name = "longitude" 
		lon:modulo = 360 
		lon:units = "degrees_east" 
		lon:_FillValue = -999 
		lon:valid_range = -180 180 
		lon:minimum = -99.9958 
		lon:maximum = -20.0042 
		lon:increment = 0.00833333 
	short elevation(lat,lon), shape = [12000 9600]
		elevation:_coordinateSystem = "lat lon " 
		elevation:long_name = "Elevation" 
		elevation:standard_name = "height" 
		elevation:units = "meters" 
		elevation:_FillValue = -32768 s
		elevation:valid_range = -13802 6543 s


//global attributes:
		:title = "Digital Elevation Model Derived from SRTM30_PLUS" 
		:institution = "IMCS, Rutgers University" 
		:institution_url = "http://marine.rutgers.edu/" 
		:history = "10-May-2005 10:08:11:  NetCDF version created by jevans
Land topography and bathymetry data from the SRTM30_PLUS V1.0 
data set of November 11, 2004, created by Joseph J. Becker jjbecker@ucsd.edu 
and David T. Sandwell. Grid resolution is 30 minutes or roughly 1 km.  Data 
and documentation are available at 
ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/SRTM30.  Land data are based on 1-km 
averages from the NASA Shuttle Radar Topography Mission. Ocean data are based 
on the Smith and Sandwell global 2-minute grid with higher resolution data from 
the NGDC Coastal Relief Model. This regional subset was extracted from the 
original data by Jay O'Reilly and John Wilkin." 
		:source = "spaceborne observation, NGDC Coastal Relief Model" 
		:comment = "Convertion to NetCDF made with MATLAB " 
		:references = "ftp://e0mss21u.ecs.nasa.gov/srtm/SRTM30" 
		:Conventions = "CF-1.0" 
		:Contact = "John Wilkin (wilkin@marine.rutgers.edu), John Evans (jevans@marine.rutgers.edu)" 
}
                

So you can see that the m-file nc_dump.m basically does the same thing as ncdump of the netCDF source distribution.