Any way to disable word splitting in bash?

Question

I'm not a bash expert but I've been working on quite a long a bash script lately and it's been getting really bothersome quoting my parameters every single time. Is there any way to change this shell behavior? I would like my strings to not be split even when I don't quote them

P.S - setting IFS to null doesn't do the job because then all arguments gets mangled. what I want is that when writing:

func1() {
    echo $1 $2 $3
}
func2() {
    echo "number of arguments func2 got: $#"
}
func2 $(func1 firstarg "second arg is a multi word string" "third arg is also a multi word string")

would print:

number of arguments func2 got: 3

Edit, thanks for comments for pointing out: since my example is using echo the code would anyway print it got either 1 or 14 arguments depending if you quote the argument to func2 or not. However what I was looking for is a way to return multiple values from a function, without them being mangled, as in the expected result I mentioned

Thanks!

Answer 1

To answer the question in the title, the way to disable word splitting is to set IFS to the empty string.

But what you described in the text was harder, to keep more than one multi-word string distinct after passing them through a command substitution. And there's really no simple way to do that.

The root issue here is that the result of a command substitution (~ the output to stdout of the function called within it) is just a single string (stream of bytes), and you're trying to fit multiple strings in it. In the general case, with arbitrary contents in those strings, that's a rather fundamental problem.

The also isn't too different from storing a command in a variable, just we have command substitution here instead.

---

A workaround would be to reserve some character to use as a separator, and set IFS to that. With the default IFS, you'd have space, tab and newline as such separators, which obviously doesn't work for strings with whitespace. With IFS set to the empty string, you'd have no such separator, so you'd always get just one field.

But you could set IFS to e.g. just the newline (assuming your strings aren't multi-line):

#!/bin/bash
IFS=$'\n'
foo() {
    printf "%s\n" "$@"
}
nargs() {
    echo "number of arguments nargs got: $#"
}
nargs $(foo firstarg "multi word string" "also a multi word string")

(You can't use empty strings at the end of the list, though, since the command substitution removes all trailing newlines regardless of IFS.)

Another way is to not use the standard output of a function, but instead pass the name of a variable to the function, and have the function write to the named array via a nameref:

#!/bin/bash
bar() {
    declare -n _out="$1"
    shift
    _out=("$@")
}
nargs() {
    echo "number of arguments nargs got: $#"
}
bar tmparr firstarg "multi word string" "also a multi word string"
nargs "${tmparr[@]}"

(There's some issues with variable scoping here if a variable called _out exists outside the function too.)

Also note that if you have unquoted expansions (variables or command substitutions), their results will also be subject to filename globbing, so an output like 12 * 34 would get badly mangled, unless you also disable globbing with set -f.

Answer 2

What you originally wanted was to disable word splitting after parameter expansion, so instead of writing

mcd() {
  mkdir -p "$1"
  cd "$1"
}

you could write

mcd() {
  mkdir -p $1
  cd $1
}

and it would work with mcd "foo bar" anyhow.

This is the preferred behaviour for most use cases, that's why zsh made it the default behaviour (you can disable it globally with the SH_SPLIT_WORD option or individually by writing ${=1}).

I know you asked for a bash solution, but "use zsh instead of bash" was the answer to so many of my questions, that I really switched to zsh one day and got rid of many problems. Thus, I gladly pass that recommendation to anyone else. IMHO there are few reasons for sticking to bash.