Adding to arrays

Question

I have this script

tests=()
igrepy -l $1 . | while read -r line
do
    // some processing
    tests+=("${second[0]}")
done
echo ${tests[@]}

I've checked that 'second' has a result and it does, however my echo returns a blank string. What has gone wrong here? This is on rhel6, 'igrepy' is an alias to a case insensitive grep that only search python files

That script fragment won't work; there's nothing before the do (eg a while or similar). — Stephen Harris, Sep 14 '16 at 16:14
The igrepy command is definitely returning results, and indeed after processing those results (into the 'second' var) it still has a non-empty value. Adding the declare statement returned "declare -a tests='()'", however I have put echos inside the loop and those came out too — Madden, Sep 14 '16 at 16:24
Incidentally, any variable reference with @ must be quoted for it to work as it should. So your last line should have been echo "${tests[@]}". But that won't solve the underlying issue - see the answers from the duplicate questions for that. — Chris Davies, Sep 14 '16 at 22:09

score 4 · Accepted Answer · answered Sep 14 '16 at 16:27

The problem you are seeing is the standard "pipe creates subshell" with bash.

eg if you do

a=10
echo 100 | read a
echo $a

then a will still be set to 10 with bash.

In your case you have

igreppy | while read ...
do
  ....
done

and all the stuff inside that while loop will be in a subshell.

Instead it can be rewritten using process substitution

while read ...
do
  ....
done < <(igreppy ...)

Now no subshell is created for the while loop.

Adding to arrays

1 Answers1