Question

There is this code:

test2.cpp (compiled to test2 executable):

#include <iostream>

int main(int argc, char** argv)
{
   for(int i = 0; i < argc; ++i){
      std::cout << i << " " << argv[i] << std::endl;
   }
   return 0;
}

test.sh (parameters preparing script):

some_array=("text1" "text two" "text tree")

input_variables=""

for i in $(seq 0 $((${#some_array[*]} - 1))); do
   input_variables="$input_variables --parameter=\"${some_array[$i]}\""
   echo $input_variables
done

echo "Running: ./test2$input_variables"
./test2 $input_variables

Output:

$ sh test.sh
--parameter="text1"
--parameter="text1" --parameter="text two"
--parameter="text1" --parameter="text two" --parameter="text tree"
Running: ./test2 --parameter="text1" --parameter="text two" --parameter="text tree"
0 ./test2
1 --parameter="text1"
2 --parameter="text
3 two"
4 --parameter="text
5 tree"

I would like to pass to test2 executable 3 arguments but 5 arguments are passed and there is a problem with space character between words. I would like also to keep input parameters in array like it is presented in *some_array* so I can add there something whenever I want. How to pass these parameters correctly?

Answer 1

Embedding quotes (or escapes) in a variable’s value doesn’t do anything useful. Quotes are parsed before variables are replaced, so by the time the quotes get there it’s too late for them to do anything (see BashFAQ #050 for more examples). And BTW using echo to print a command is extremely misleading, use set -x to have the shell print what it thinks is going on.

The best thing to do, as you said in your final note, is to store the parameters in an array:

#!/bin/bash
some_array=("text1" "text two" "text tree")

input_variables=()

for i in $(seq 0 $((${#some_array[*]} - 1))); do
   input_variables+=("--parameter=${some_array[$i]}")
   echo "${input_variables[@]}"
done

printf "Running:"
printf " %q" ./test2 "${input_variables[@]}"
./test2 "${input_variables[@]}"

BTW, arrays are a bash extension, and not always available in plain shells, so you should run this with bash, not sh.