How to preserve double quotes in $@ in a shell script?

Question

Let\'s say I have a really simple shell script \'foo\':

  #!/bin/sh
  echo $@

If I invoke it like so:

  foo 1 2 3
         


        

Answer 1

Let's suppose you are in a more rigid set-up and you CANNOT change your command line, and make it more "friendly" by escaping the double quotes. For example:

example_script.sh argument_without_quotes "argument with quotes i cannot escape"

First consider that inside your script you can't tell if an argument is passed with or without quotes, because the shell strips them.

So what you can possibly do is rebuilding double quotes for arguments containing whitespaces

This example rebuilds the whole command line, double-quoting arguments that have white spaces

#!/bin/sh
#initialize the variable that will contain the whole argument string
argList=""
#iterate on each argument
for arg in "$@"
do
  #if an argument contains a white space, enclose it in double quotes and append to the list
  #otherwise simply append the argument to the list
  if echo $arg | grep -q " "; then
   argList="$argList \"$arg\""
  else
   argList="$argList $arg"
  fi
done

#remove a possible trailing space at the beginning of the list
argList=$(echo $argList | sed 's/^ *//')

#pass your argument list WITH QUOTES
echo "my_executable" $argList
#my_executable $argList

Note this limitation. If you run this example

example_script.sh "argument with spaces" argument_without_spaces "argument_doublequoted_but_without_spaces"

you will get this output

my_executable "argument with spaces" argument_without_spaces argument_doublequoted_but_without_spaces

Note the last argument: since it had no spaces, it has not been enclosed again in double quotes, but this shouldn't be an issue.