How to interate through command line arguments saved in a variable?

Question

At some point in my script I need to save value of all command line arguments in a variable (after some shifting), it looks like this:

foo="$@"

Now I need to interate through the arguments from foo variable, but it seems to be quite hard to do it properly if there are arguments containing write space. If I write

for i in "$foo"
do
    echo "$i"
done

Everything is printed on one line, indicating that for thinks there is only one argument. On the other hand:

for i in $foo
do
    echo "$i"
done

seems to do the right thing, but it fails too when there are arguments containing write space:

$ my_script one two "three four"
one
two
three
four

In this example three and four should be printed on the same line.

How to iterate though arguments saved in a variable properly?

Related: How to iterate over list which contains whitespaces in bash — fedorqui
– fedorqui, Commented Apr 28, 2015 at 13:38

Wintermute · Accepted Answer · 2015-04-28 13:35:19Z

2

You could use bash arrays:

foo=("$@")

for i in "${foo[@]}"; do
    echo "$i"
done

This also allows you to address individual arguments as ${foo[0]}, ${foo[1]}, and so forth, up to ${#foo[@]}, which is the length of the array.

Note that arrays are bash-specific (not part of the POSIX shell language).

answered Apr 28, 2015 at 13:35

Wintermute

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4 Comments

Mark Karpov Over a year ago

Great. The only problem is that it's bash specific. But it's not critical for me. Thanks!

glenn jackman Over a year ago

@Mark, you tagged your question with bash, so don't be surprised to get bash answers.

Mark Karpov Over a year ago

@glennjackman, good point. Next time I will tag it with [shell] too ;-)

Wintermute Over a year ago

@Mark The implementation of something vaguely array-ish in POSIX shell that is not painful to both write and to use is, as far as I'm aware, an unsolved problem. It'll generally involve something like eval set -- "$array" to expand the array into the positional variables, and doing that requires meticulous quoting with special care given to single quotes within the arguments. If you find yourself in a position where you need it and can't rely on bash, consider using another programming language. Perl comes to mind -- boxes that don't have it are few and far between these days.

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