Creating array of objects in bash

Question

Is it possible to create an array of objects in bash?

That's how I'm trying:

declare -a identifications=(
  {
    email    = '...',
    password = '...'
  }
)

declare -a years=(
  '2011'
  '2012'
  '2013'
  '2014'
  '2015'
  '2016'
)

for identification in "${identifications[@]}"
do
  for year in "${years[@]}"
  do
    my_program --type=CNPJ --format=XLS --identification=${identification.email} --password=${identication.password} --competence=${year} --output="$identification - $year"
  done
done

Obviously, this doesn't work, and I'm not finding how to achieve that, since I'm not finding bash objects.

Answer 1

You could do some trickery with associative arrays (introduced in Bash 4.0) and namerefs (see manual for declare and the first paragraph of Shell Parameters – introduced in Bash 4.3):

#!/usr/bin/env bash

declare -A identification0=(
    [email]='[email protected]'
    [password]='admin123'
)
declare -A identification1=(
    [email]='[email protected]'
    [password]='passwd1!'
)

declare -n identification
for identification in ${!identification@}; do
    echo "Email: ${identification[email]}"
    echo "Password: ${identification[password]}"
done

This prints

Email: [email protected]
Password: admin123
Email: [email protected]
Password: passwd1!

declare -A declares an associative array.

The trick is to assign all your "objects" (associative arrays) variable names starting with the same prefix, like identification. The ${!prefix@} notation expands to all variable names starting with prefix:

$ var1=
$ var2=
$ var3=
$ echo "${!var@}"
var1 var2 var3

Then, to access the key-value pairs of the associative array, we declare the control variable for the for loop with the nameref attribute:

declare -n identification

so that the loop

for identification in ${!identification@}; do

makes identification behave as if it were the actual variable from the expansion of ${!identification@}.

In all likelihood, it'll be easier to do something like the following, though:

emails=('[email protected]' '[email protected]')
passwords=('admin123' 'passwd1!')
for (( i = 0; i < ${#emails[@]}; ++i )); do
    echo "Email: ${emails[i]}"
    echo "Password: ${passwords[i]}"
done

I.e., just loop over two arrays containing your information.

Answer 2

I tend to use json to create objects. For me it makes it really easy and flexible.

Here is a oversimplified example.

I create a json file: devices.json

{
          "backup" : [{
                "addr":"192.168.1.1",
                "username":"backuper",
                "dstfile":"firewallconfig",
                "ext":".cfg",
                "method":"ssh",
                "rotate":"no",
                "enabled":"yes"
            }, {
                "addr":"192.168.1.2",
                "username":"backuper",
                "dstfile":"routerconfig",
                "ext":".cfg",
                "method":"ssh",
                "rotate":"no",
                "enabled":"yes"
            }]
 }

Bash script: task.sh

 # read the devices.json file and store it in the variable jsonlist
    jsonlist=$(jq -r '.backup' "devices.json")
        # inside the loop, you cant use the fuction _jq() to get values from each object.
        for row in $(echo "${jsonlist}" | jq -r '.[] | @base64'); do
            _jq()
            {
             echo ${row} | base64 --decode | jq -r ${1}
            }
         
        echo "backing up: $(_jq '.addr')"
        echo "using method: $(_jq '.method')"
        done

The guy who posted the original post can be found by googling "using json with bash" or something.