Accessing Associative Arrays in GNU Parallel

Question

Assume the following in Bash:

declare -A ar='([one]="1" [two]="2" )'
declare -a ari='([0]="one" [1]="two")'
for i in ${!ari[@]}; do 
  echo $i ${ari[i]} ${ar[${ari[i]}]}
done
0 one 1
1 two 2

Can the same be done with GNU Parallel, making sure to use the index of the associative array, not the sequence? Does the fact that arrays can't be exported make this difficult, if not impossible?

Answer 1

A lot has happened in 4 years. GNU Parallel 20190222 comes with env_parallel. This is a shell function that makes it possible to export the most of the environment to the commands run by GNU Parallel.

It is supported in ash, bash, csh, dash, fish, ksh, mksh, pdksh, sh, tcsh, and zsh. The support varies from shell to shell (see details on https://www.gnu.org/software/parallel/env_parallel.html). For bash you would do:

# Load the env_parallel function
. `which env_parallel.bash`
# Ignore variables currently defined
env_parallel --session
[... define your arrays, functions, aliases, and variables here ...]
env_parallel my_command ::: values
# The environment is also exported to remote systems if they use the same shell
(echo value1; echo value2) | env_parallel -Sserver1,server2 my_command
# Optional cleanup
env_parallel --end-session

So in your case something like this:

env_parallel --session
declare -A ar='([one]="1" [two]="2" )'
declare -a ari='([0]="one" [1]="two")'
foo() {
  for i in ${!ari[@]}; do 
    echo $i ${ari[i]} ${ar[${ari[i]}]}
  done;
}
env_parallel foo ::: dummy
env_parallel --end-session

As you might expect env_parallel is a bit slower than pure parallel.