Create array in bash dynamically

Question

I would like to create and fill an array dynamically but it doesn't work like this:

i=0
while true; do
    read input
    field[$i]=$input
    ((i++))
    echo {$field[$i]}  
done

What is your actual problem? Aside from some minor issues, your code is fine. — ormaaj
– ormaaj, Commented Nov 7, 2012 at 19:38
It works like a simple variable. If I the input is test, it echo: {test[0]} — Sadiel
– Sadiel, Commented Nov 7, 2012 at 19:44
I don't see any echo there. You just have an infinite loop that appends an array and does nothing with it. Yes expanding "$test" is always equivalent to "${test[0]}" (even if test isn't an array). — ormaaj
– ormaaj, Commented Nov 7, 2012 at 19:51

Mat · Accepted Answer · 2012-11-07 19:43:13Z

20

Try something like this:

#! /bin/bash
field=()
while read -r input ; do
    field+=("$input")
done
echo Num items: ${#field[@]}
echo Data: ${field[@]}

It stops reading when no more input is available (end of file, ^D in the keyboard), then prints the number of elements read and the whole array.

answered Nov 7, 2012 at 19:37

Mat

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Comments

chepner · Accepted Answer · 2018-05-13 21:08:49Z

19

The assignment is fine; the lookup is wrong:

echo "${field[$i]}"

answered Nov 7, 2012 at 20:52

chepner

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ormaaj · Accepted Answer · 2012-11-07 19:33:46Z

2

i= field=()
while :; do
    read -r 'field[i++]'
done

Is one way. mapfile is another. Or any of these. However what you've posted is valid.

answered Nov 7, 2012 at 19:33

ormaaj

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