#minimum
cat your_data_file.dat | sort -nk3,3 | head -1 
                            #this will find minumum of column 3
#maximun 
cat your_data_file.dat | sort -nk3,3 | tail -1
                        #this will find maximum of column 3 
#to find in column 2 , use -nk2,2 

#assing to a variable and use 
min_col=`cat your_data_file.dat | sort -nk3,3 | head -1 | awk '{print $3}'`