Nx : 1600;
Ny : 400;
dx : .524584;
dy : .25;
dt : 1;

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, char * argv[])
{
if(argc!=2)
{
    printf("ERROR:  Usage: ./Practice3 <input file>");
}
else
    {
FILE * fr = fopen(argv[1], "rt");


if(fr == NULL){printf("file %s not found", argv[1]);}

char * tmpstr1 ;
char * tmpstr2 ;

char * delimPtr;
char * endPtr;

int Nx = 0;
int Ny = 0;
double dx = 0;
double dy = 0;

    char tempbuff[100];

    while(!feof(fr))
    {
         if (fgets(tempbuff,100,fr)) {

            delimPtr = strstr(tempbuff,":");
            endPtr = strstr(delimPtr,";");
            strncpy(tmpstr1,tempbuff,delimPtr-tempbuff);
            strncpy(tmpstr2,delimPtr+2 ,endPtr-delimPtr-2);
            printf("<<%s>>n",  tmpstr1);
            printf("<<%s>>n",  tmpstr2);

            if (strcmp(tmpstr1,"Nx")==0) {
                 Nx = atoi(tmpstr2);
            }
            else if (strcmp(tmpstr1,"Ny")==0) {
                 Ny = atoi(tmpstr2);
            }
            else if (strcmp(tmpstr1,"dx")==0) {
                 dx = atof(tmpstr2);
            }
            else if (strcmp(tmpstr1,"dy")==0) {
                 dy = atof(tmpstr2);
            }
            else{
                printf("Unrecongized parameter : "%s"n", tmpstr1);
            }


         }


    }


    fclose(fr);

    printf("nNx : %d nNy : %d  ndx : %f  ndy : %f n",  Nx,Ny,dx,dy);


}//end of code executed when input is correct


}

char tmpstr1[16];
char tmpstr2[16];
...
/*
delimPtr = strstr(tempbuff,":");
endPtr = strstr(delimPtr,";");
strncpy(tmpstr1,tempbuff,delimPtr-tempbuff-1);
strncpy(tmpstr2,delimPtr+2 ,endPtr-delimPtr-2);
*/
sscanf(tempbuff, "%15s : %15[^;];", tmpstr1, tmpstr2);