Labelling of text files in bash loop

Question

This script should give values to the program through the command line and store the output of the terminal in their corresponding files. Since I cannot put a decimal-point number as part of the label of the file, I intent to multiply each kappa by 10000 to turn them into integers and use them as labels, but I did it wrong in the code and I don't know how to it properly. How does it work? Thank you!

#!/bin/bash

for kappa in $(seq 0.0001 0.000495 0.01);
    do
        kappa_10000 = $kappa * 10000;

        for seed in {1..50};
        do
                ./two_defects $seed $kappa > "equilibration_step_seed${seed}_kappa${kappa_10000}.txt";
        done
    done

First thing that jumps out is line 5, `kappa_10000 = $kappa * 10000`. In Bash, don't put spaces around the equals sign. Also, you're calling the math part wrong. `kappa_10000=$((kappa * 10000))` — Guest, Jan 23 '17 at 09:08
An interesting and extensive cross-site duplicate [here](http://unix.stackexchange.com/questions/40786/how-to-do-integer-float-calculations-in-bash-or-other-languages-frameworks). — Aserre, Jan 23 '17 at 09:29
It is very important what you said about spaces around the equal sign! I noticed this also when playing on the terminal! But you can't do floating-point arithmetic in bash. Thanks Guest — , Jan 23 '17 at 09:47
Possible duplicate of [How do I use floating-point arithmetic in bash?](http://stackoverflow.com/questions/12722095/how-do-i-use-floating-point-division-in-bash) — Inian, Jan 23 '17 at 09:58
Why can't you store with the decimal point? Or replace the point with an underscore? Or use `${kappa:2}` ? — Walter A, Jan 23 '17 at 17:03
Basically because I started learning bash two days ago and I don't know anything about it yet. That was the first idea I had and I wanted to work it out @WalterA — , Jan 24 '17 at 07:37

score 2 · Answer 1 · edited Jan 23 '17 at 12:01

Bash does not do floating-number calculation as pointed out by @Inian. A program like bc must be called and its output can be directly stored in a variable as follows:

for kappa in $(seq 0.0001 0.000495 0.01)
do 
    kappa_10000=$(echo "$kappa*10000/1" | bc)
    echo kappa_10000
done

The output in the terminal would be

The /1 operation must be added to make the output an integer.

Labelling of text files in bash loop

1 Answers1