Bash array isn't working?

Question

The following code is not outputting anything.

#!/bin/bash
declare -A a
cat input.txt | while read item value
do
if [ $item="owner" ] || [ $item="admin" ] || [ $item="loc" ] || [ $item="ser"]
then
a[$item]=$value
fi
done
echo ${a[owner]}

the input file is:

owner sysadmin group
admin ajr
loc S-309
ser 18r97
comment noisy fan

I need to create an array a only for index at owner, admin, loc and ser.

I was expecting an output for echo ${a[owner]} to be sysadmin group and so on.

Any help?

EDIT: I think it might have something to do with owner is sysadmin group, how do I read that (two words with space) into a variable (value)?

possible duplicate stackoverflow.com/questions/1789750/scope-of-variable-in-pipe — Nehal J Wani
– Nehal J Wani, Commented Feb 7, 2014 at 22:45

anubhava · Accepted Answer · 2014-02-07 22:41:06Z

1

It is because you're using a sub-shell by using pipe. All the changes made in the sub-shell are local to sub shell only and not reflected in parent shell.

Use this:

#!/bin/bash
declare -A a
while read item value
do
  if [ $item="owner" ] || [ $item="admin" ] || [ $item="loc" ] || [ $item="ser"]
  then
    a[$item]=$value
   fi
done < input.txt

echo ${a[owner]}
sysadmin group

answered Feb 7, 2014 at 22:41

anubhava

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5 Comments

Nick Over a year ago

The actual assignment for us is to write a script that will output something like that in a table, but on multiple files from a directory, the script expects a single command line argument which is the directory. So I am trying to write this part that will open a file and store them into the array, and call it later on to do the table. From my understanding I cant pipe cat here with while read, how should I do it otherwise?

anubhava Over a year ago

I have provided you working code. Instead of pipe use done < file to read it.

Nick Over a year ago

Ah, right, done <file should do the trick, I totally missed that part, thank you!

Nick Over a year ago

One more question, if I need to do a loop for the above code and have it work on every file in a given directory, and the array names will be the file name instead of a, how does that work? I tried using a for loop but it didn't quite work.

anubhava Over a year ago

Creating dynamic array names is not trivial. See my answer here for more details: stackoverflow.com/a/21626692/548225

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