0 
for i in "a" "a b"; do
    echo $i;
done

echoes:

a
a b

How can I write something like for i in $input; do and assign "a" "a b" to input? The whitespace is important. Otherwise $(echo ...) would work.

Edit: The question is not about files and neither about some input, which can be caught using $@.

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2 Answers 2

Reset to default
4

Since you're using bash, you could do this:

input=("a" "a b")

for i in "${input[@]}"; do
  echo $i
done
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17 Comments

@Zack The question is tagged as bash. Are we now requiring that, in addition to being correct, answers need to be POSIX conformant, even if the OP asks for bash?
You should have at least noted them as nonstandard. But it is my considered opinion that one should never use bashisms: if there is no way to accomplish something in portable shell, the correct choice is to use Perl or Python instead.
@Zack Right. Even if a script is never meant to be used by anybody but the OP, in an environment that they control, they're not allowed to use "bashisms", despite the fact that "bashisms" are shorter, faster, and less quirky than POSIX standard shell. The question is not "What's the best tool for this job?" the question is "How do you accomplish this is bash?" If the OP wanted a lecture on the virtues of python over the shell he could go read about it on the myriad of sites that discuss that issue.
@Zack: Then let us all immediately uninstall Bash. And Python 3 and Python 2.6 or later or anything later than Perl 5.8. ...There is a time for portability and there's a time when it doesn't matter or the more powerful, newer features are more powerful and more necessary. Yes, it's true, it's important to know the difference (or when to use something else entirely), but every question about Bash should not trigger a compulsion to hawk portability or "use something else" unless it's pertinent to the question.
Not sure why there is so much hostility towards portability. You would think that the troubles encountered trying to change /bin/sh from bash on Debian would have sufficiently demonstrated that portability really is important. It is important to mention it in any question tagged shell or explicitly bash because many people are not even aware that there is an issue.
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1

This can only be done portably with the "$@" construct for command-line arguments.

However, if you don't need the actual command line arguments anymore, you can use set to replace their contents:

input='"a" "a b"'
eval set fnord $input
shift
for i in "$@"; do
    echo $i
done

You should be aware that merely having asked this question suggests that you are approaching the complexity level where you should switch to a less limited scripting language (Perl and Python are the usual choices).

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3 Comments

shell functions get their own command line params, so it doesn't blow away the original args. echoi() { for i in "$@"; do echo $i; done; } echoi "a" "a b"
That's good if the surrounding context allows you to use a shell function, but sometimes that's not an option; we don't know what the OP's larger situation is.
Note that this is such a common idiom, it is the default. You can omit in "$@ and just write: for i; do echo $i; done

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