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HOME > Monitoring_and_Data > Oceanic and Atmospheric Data > Reanalysis: Atmospheric Data > wgrib2

wgrib2: a sample function


Wgrib2 is "function" driven. Every option on the command line now calls a function. Each function is called several times, for initialization (mode=-1), for each grib record (mode=0,1,2 depending on the verbosity index) and for clean up (mode=-2). Here is a sample function.

#include <stdio.h>
#include "grb2.h"
#include "wgrib2.h"
#include "fnlist.h"

extern int decode;
extern int need_output_file;

* HEADER:100:min:inv:0:print minimum value
* the above line is needed by each command line option
* HEADER:sort-order:type-of-function:number-of-arguments:description

int f_min(int mode, unsigned char **sec, float *data, int ndata, FILE *out) {
   double mn;
   int ok, i;

   if (mode == -1) decode = 1;
   else {
     mn = ok = 0;
     for (i = 0; i < ndata; i++) {
       if (!UNDEFINED_VAL(data[i])) {
         if (ok) mn = mn < data[i] ? mn : data[i];
         else { ok = 1; mn = data[i]; }
     if (ok) printf("min=%lg",mn);
     else printf("min=undefined");
   return 0;

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Page last modified: May 15, 2005
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