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In addition to all its interactive functionality, Metview can be run in a purely batch mode from the command line. Of course, in this mode we cannot have an interactive plot window, but we can save plots in various formats (see Working with graphical output) and we can save computed data into files of various formats (see Processing Data).
Metview runs in batch mode when the option -b is specified when you first call it. You can run Metview in batch mode while having a Metview interactive session up and running - they will not interfere with each other. To run a macro in batch mode simply specify its name on the command line after the -b option:
% metview -b macro_name [arg1 arg2 ...] |
where macro_name is the name of the macro you want to run. You can specify a path to the macro if it is not in the current directory.
The arguments() function returns a list of command-line arguments.
Write a short new Macro which requires a single argument (a meteorological parameter short name such as Z, T or RH) to be passed to it on the command line. It should fail if more or less arguments are passed. It should print the argument that has been passed to it. Useful hints:
count() function returns the number of elements in a listfail() function takes a string as its argument and will print the string and exit Metview with an error codeExpand the macro to retrieve this parameter from MARS on a 1x1 degree grid. The only parameters required to be set in the retrieve() function are Parameter and Grid. You can use the print() function to confirm that the fields have been retrieved.
Note that the additional command-line argument -slog tells Metview to provide more output - this can be useful to diagnose problems. This argument (and indeed all other arguments) must come before the -b, and anything after it will be interpreted as an argument to your macro. |
Environment variables can be queried, not only in batch mode but also in interactive mode. This can be an alternative way to pass information to a macro.
In a macro, get the value of a chosen environment variable (e.g. HOST) using the getenv() function. For example:
machine = getenv('HOST')
print('Running on ', machine) |
The macro function runmode() returns a string which tells us the mode in which it has been run. If the return value is "batch" then Metview has been invoked in batch mode.
Add a check to your macro: if it is running in batch mode, then take the parameter from the command line arguments as before; otherwise, set it to some string of your choosing. In both cases, the name should be printed. Try running the macro in batch mode, and also from the Macro Editor.
If running in interactive mode (i.e. not "batch") then plot the data to an interactive Display Window. If in batch mode, plot the data to a PostScript file called my_field.ps. See Working with graphical output for more detail if required.
Metview has a shortcut for invoking the data examiners from the command line for quick data inspection.
Find a GRIB file somewhere in your Metview directory structure (it can also be outside the Metview home directory). From the command-line, type:
metview -e grib /path/to/grib |
This works for GRIB, BUFR, ODB and netCDF files. The file type must be the first argument.
For the same GRIB file, from the command-line, type:
metview -p /path/to/grib |
This gives a quick way to plot a file outside the Metview environment. The visualisation uses the same settings as ecCharts, so depending on the meteorological parameter you will get different contouring styles.
Take some of the macros you've already written and convert them so that they can run in batch mode. In most cases it will not require much work - here are the main things to consider: