bash create for loop with an array variable

Question

i am trying to make output of a command be read by a for loop, but in such a way that the loop variable would be an array. is that possible? this is what I've been trying so far:

function samplevals() {
    echo '"aa bb"'
    echo '"cc dd"'
    echo '"ee ff" "gg hh"'
}

samplevar='"aa bb"
"cc dd"
"ee ff" "gg hh"'

echo call function samplevals:
for x in `samplevals `; do echo ">$x<"; done

echo read variable samplevar:
echo $samplevar
for x in $samplevar; do echo ">$x<"; done

echo process output of 'echo samplevar:'
for x in `echo $samplevar`; do echo ">$x<"; done

echo "the thing with set"
for x in $samplevar; do set -- $x ; echo "\$1=>$1<,\$2=>$2<"; done

but the output is always the same:

>"aa<
>bb"<
>"cc<
>dd"<
>"ee<
>ff"<
>"gg<
>hh"<

Can I somehow prevent bash from splitting the elements into smaller pieces?

The quotes are literal data, not syntactic quotes. You don't have any arrays in your code. — chepner
– chepner, Commented Jan 11, 2017 at 13:24

Community · Accepted Answer · 2017-05-23 11:45:49Z

1

Along the lines of chepner's answer, using read command. The -a flag part of the command lets the output to written out to an array.

IFS=$'\t' read -ra arrayDef < <(echo -ne '"abc def"\t"ghi jkl"')
for x in "${arrayDef[@]}"; do
    echo ">$x<"
done

You can replace the echo part with some command that generates such a string. Remember to update the IFS appropriately as to how the string is de-limited. In my case, I just a have the string de-limited by \t

edited May 23, 2017 at 11:45

CommunityBot

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answered Jan 11, 2017 at 13:34

Inian

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2 Comments

chepner Over a year ago

This just shifts the "delimiter" from arbitrary whitespace to a tab specifically. It doesn't solve the underlying problem of having a separator that is guaranteed not to occur in an element of the array.

Inian Over a year ago

@chepner: Initially provided this as alternative complementing logic on seeing yours, but on seeing OP not approving of yours. Do you want me to delete it

chepner · Accepted Answer · 2018-10-31 17:14:27Z

1

The way to define an array in bash is

samplevars=("aa bb" "cc dd" "ee ff" "gg hh")
for x in "${samplevars[@]}"; do
    echo ">$x<"
done

edited Oct 31, 2018 at 17:14

answered Jan 11, 2017 at 13:26

chepner

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2 Comments

chepner Over a year ago

There is no simple way to create an array from command output, because there is no such thing as an array value in bash, only array parameters whose syntax gives the appearance of array values. An array is really closer to a loosely related set of individual variables, tied together with some syntactic sugar.

MathKid Over a year ago

This almost works. Change samplevars to samplevar on the first line.

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