Shell loops using non-integers?

Question

I wrote a .sh file to compile and run a few programs for a homework assignment. I have a "for" loop in the script, but it won't work unless I use only integers:

#!/bin/bash
for (( i=10; i<=100000; i+=100))
do
    ./hw3_2_2 $i
done

The variable $i is an input for the program hw3_2_2, and I have non-integer values I'd like to use. How could I loop through running the code with a list of decimal numbers?

Answer 1

The easiest way is to just list them:

for a in 1.2 3.4 3.11 402.12 4.2 2342.40
do
  ./hw3_2_2 $a
done

If the list is huge, so you can't have it as a literal list, consider dumping it in a file and then using something like

for a in $(< my-numbers.txt)
do
  ./hw3_2_2 $a
done

The $(< my-numbers.txt) part is an efficient way (in Bash) to substitute the contents of the names file in that location of the script. Thanks to Dennis Williamson for pointing out that there is no need to use the external cat command for this.

Answer 2

bash doesn't do decimal numbers. Either use something like bc that can, or move to a more complete programming language. Beware of accuracy problems though.

Answer 3

Here's another way. You can use a here doc to include your data in the script:

read -d '' data <<EOF
1.1
2.12
3.14159
4
5.05
EOF

for i in $data
do
    ./hw3_2_2 $i
done

Similarly:

array=(
1.1
2.12
3.14159
4
5.05
)

for i in ${array[@]}
do
    ./hw3_2_2 $i
done

Answer 4

you can use awk to generate your decimals eg steps of0.1

num=$(awk 'BEGIN{for(i=1;i<=10;i+=0.1)print i}')
for n in $num
do
  ./hw3_2_2 $n
done

or you can do it entirely in awk

awk 'BEGIN{cmd="hw3_2_2";for(i=1;i<=10;i+=0.1){c=cmd" "i;system(cmd) } }'