回显一个引用的引用数组

Question

The following code

myopts=( --url="http://www.lemonde.fr" --out="hello world" --out-format="png" )
echo "going to execute following command: cutycapt ${myopts[@]}"
# commented out because this way you do not have to have cutycapt to test
# cutycapt "${myopts[@]}"

outputs the following:

going to execute following command: cutycapt --url=http://www.lemonde.fr --out=hello world --out-format=png

but really what is executed is:

cutycapt --url="http://www.lemonde.fr" --out="hello world" --out-format="png"

Thus, that is what I would like to be output from the echo command.

Answer 1

When you create your array, its elements are subject to quote removal. If you want to keep them, you have to add them quoted already:

$ myopts=( '--url="http://www.lemonde.fr"' '--out="hello world"' '--out-format="png"' )
$ echo "going to execute following command: cutycapt ${myopts[@]}"
going to execute following command: cutycapt --url="http://www.lemonde.fr" --out="hello world" --out-format="png"

If you look at your array elements after creating myopts , you'll see that they're already missing the quotes:

$ myopts=( --url="http://www.lemonde.fr" --out="hello world" --out-format="png" )
$ (IFS=$'\n'; echo "${myopts[*]}")
--url=http://www.lemonde.fr
--out=hello world
--out-format=png

So it's not the expansion that removes them – it happens when assigning.

Answer 2

You can use printf with the %q format string to print a quoted version of the arguments like

printf '%q ' cutycapt "${myopts[@]}"; printf '\n'

(we add our \\n to the end since printf doens't automatically add one)

Example:

$ myopts=( --url="http://www.lemonde.fr" --out="hello world" --out-format="png" )
$ printf 'going to execute following command: '; printf '%q ' cutycapt "${myopts[@]}"; printf '\n'
going to execute following command: cutycapt --url=http://www.lemonde.fr --out=hello\ world --out-format=png

with the escape of the space in hello world

Depending on why you want this, have you considered just running with set -x enabled, so you see the expanded command line before it's executed anyway?

$ set -x
$ cutycapt "${myopts[@]}"
+ cutycapt --url=http://www.lemonde.fr '--out=hello world' --out-format=png