How can i populate an array in loop? I'd like to do something like that:
declare -A results
results["a"]=1
results["b"]=2
while read data; do
results[$data]=1
done
for i in "${!results[@]}"
do
echo "key : $i"
echo "value: ${results[$i]}"
done
But it seems that I cannot add anything to an array within for loop. Why?
What you have should work, assuming you have a version of Bash that supports associative arrays to begin with.
If I may take a wild guess . . . are you running something like this:
command_that_outputs_keys \
| while read data; do
results[$data]=1
done
? That is — is your while loop part of a pipeline? If so, then that's the problem. You see, every command in a pipeline receives a copy of the shell's execution environment. So the while loop would be populating a copy of the results array, and when the while loop completes, that copy disappears.
Edited to add: If that is the problem, then as glenn jackman points out in a comment, you can fix it by using process substitution instead:
while read data; do
results[$data]=1
done < <(command_that_outputs_keys)
That way, although command_that_outputs_keys will receive only a copy of the shell's execution environment (as before), the while loop will have the original, main environment, so it will be able to modify the original array.
while ... done < <(command here)That seems to be working fine:
$ cat mkt.sh
declare -A results
results["a"]=1
results["b"]=2
while read data; do
results[$data]=1
done << EOF
3
4
5
EOF
for i in "${!results[@]}"
do
echo "key : $i"
echo "value: ${results[$i]}"
done
$ ./mkt.sh
key : a
value: 1
key : b
value: 2
key : 3
value: 1
key : 4
value: 1
key : 5
value: 1
$
Ubuntu 11.10 here, bash: GNU bash, version 4.2.10(1)-release (x86_64-pc-linux-gnu).
