awk scientific notation input

问题

I'm having a bit of trouble with getting awk to read scientific notation from a file, here is some example input:

  #Plane   Turn   Real    Imaginary
  HOR    1    0.0000e+00    -2.1885e-07
  HOR    1    4.8481e-08    -8.1221e-08
  HOR    1    4.0934e-08    -6.0784e-08
  HOR    1    3.5707e-08    -5.1223e-08
  HOR    1    3.1664e-08    -4.5608e-08
  HOR    1    2.8268e-08    -4.1964e-08
  HOR    1    2.5242e-08    -3.9469e-08
  HOR    1    2.2429e-08    -3.7707e-08
  HOR    1    1.9731e-08    -3.6430e-08
  HOR    1    1.7082e-08    -3.5479e-08

I'm using awk to format this file for plotting with gnuplot using the following command:

gnuplot "awk '{if($2==1){printf "%.4e\n",sqrt($3^2+$4^2)}}' bathtub_values.dat" w l

However the arithmetic is not working correctly and after a few tests I realized that awk doesn't seem to correctly interpret the input format, how can I specify to awk the format to use?

回答1:

If you're not entitled to install a different awk, you can define and use a function to parse the engineering notation

% awk 'function parse_en(eng_num) {
        split(eng_num,en,/[eEdD]/); return en[1]*10**en[2]; }
     $1 !~ /#/ {
        printf "%.4e\n",sqrt(parse_en($3)^2+parse_en($4)^2)}
'  bathtub_values.dat
2.1885e-07
9.4590e-08
7.3282e-08
6.2440e-08
5.5522e-08
5.0597e-08
4.6850e-08
4.3873e-08
4.1430e-08
3.9377e-08
% 

来源：https://stackoverflow.com/questions/24517880/awk-scientific-notation-input