Spaces and curly braces for variables in bash

Question

Is there a way to make ${VAR} expand as if it were quoted in double quotes?

That's not what I wanted to see:

% A="some spaces in there"
% touch ${A}
% ls -1
in
some
spaces
there

Sure, I can use typical notation like "$VAR". But that's cumbersome when using quotes within quoted text, etc. I wonder if there's a way of expanding ${...} notation that would treat ${...} as if it were "${...}" while not using doublequotes themselves?

Answer 1

You can set the IFS variable to disregard spaces when the shell splits variables. This is also useful when taking in input that may contain spaces in loops.

$ cat /tmp/t.sh
IFS="$(printf '\n\t')"
A="some spaces in there"
touch ${A}
ls -l
$ /tmp/t.sh
some spaces in there

(If you have characters like * in your strings try a set -f to disable globbing (see help set) thanks @glenn jackman. But really, putting a * in a filename is asking for trouble!)

And the original:

$ cat /tmp/t.sh
#!/bin/bash
A="some spaces in there"
touch ${A}
ls -1
$ /tmp/t.sh 
in
some
spaces
there
$

Answer 2

Not following accepted best practice (and learning how the shell really works) is very likely to bite you. Repeatedly. With zombie virus-infected fangs. Some things which can help:

• You can use different quotes for different parts of a single parameter as long as the start and end quotes are next to each other:

  $ printf '%q\n' "foo 'bar' baz"'nuu "boo" zoo'
  foo\ \'bar\'\ baznuu\ \"boo\"\ zoo
  

• You can set IFS in a subshell to avoid screwing up your entire script:

  $ a="some spaces in there"
  $ (IFS= && touch ${a})
  $ ls -1
  some spaces in there