Subshells (GNU Parallel)

I have the impression that GNU Parallel creates a subshell and that precautions have to be taken to assure that functions and variables are available in that subshell.

Not that this subshell stuff is not the same as scope within a single shell

Without exported function or variable

################################################################################
# Subshell & vars? - Without exporting function or var
################################################################################
#
# Function
########################################
#
subfunction()
{
   echo "Subfunction - Var j: $j"
}


# Main
########################################
#
j=12
echo "Main - var j: $j"
#
parallel subfunction ::: $(seq 5)

Output:

Main - var j: 12
/bin/bash: subfunction: command not found
/bin/bash: subfunction: command not found
/bin/bash: subfunction: command not found
/bin/bash: subfunction: command not found
/bin/bash: subfunction: command not found

With exported function

Now the function is exported using export -f subfunction and GNU Parallel can find it. However, the variable j is not available within this function.

################################################################################
# Subshell & vars? - With exporting function
################################################################################
#
# Function
########################################
#
subfunction()
{
   echo "Subfunction - Var j: $j"
}


# Main
########################################
#
j=12
echo "Main - var j: $j"
export -f subfunction
#
parallel subfunction ::: $(seq 5)

Output:

Main - var j: 12
Subfunction - Var j: 
Subfunction - Var j: 
Subfunction - Var j: 
Subfunction - Var j: 
Subfunction - Var j: 

With exported function and exported variable

Juhu! Sometimes, things are easy:

################################################################################
# Subshell & vars? - With exporting function
################################################################################
#
# Function
########################################
#
subfunction()
{
   echo "Subfunction - Var j: $j"
}


# Main
########################################
#
j=12
echo "Main - var j: $j"
export -f subfunction
export j
#
parallel subfunction ::: $(seq 5)

Output:

Main - var j: 12
Subfunction - Var j: 12
Subfunction - Var j: 12
Subfunction - Var j: 12
Subfunction - Var j: 12
Subfunction - Var j: 12

But not for arrays

It seems that regular arrays and associate arrays cannot be exported to subshells:

################################################################################
# Subshell, var & arrays
################################################################################
#
# Function
########################################
#
subfunction()
{
   echo "function - Var i:               $i"
   echo "function - Associative array j: ${j[@]}"
   echo "function - Regular array k:     ${k[@]}"
}


# Main
########################################
#
i=12

declare -gA j

j[foo,1]="Foo-1"
j[bar,2]="Bar-2"

k[1]="K1"
k[2]="K2"


echo "Main - var j: $i"
export -f subfunction
export i
export j    # Doesn't work
export j[@]    # Doesn't work
export k    # Doesn't work
export k[@]    # Doesn't work
export {k[@]}  # Doesn't work
#
parallel subfunction ::: $(seq 5)

Output:

Main - var j: 12
./parallel.sh: line 181: export: `j[@]': not a valid identifier
./parallel.sh: line 183: export: `k[@]': not a valid identifier
./parallel.sh: line 184: export: `{k[@]}': not a valid identifier
function - Var i:               12
function - Associative array j: 
function - Regular array k:     
function - Var i:               12
function - Associative array j: 
function - Regular array k:     
function - Var i:               12
function - Associative array j: 
function - Regular array k:     
function - Var i:               12
function - Associative array j: 
function - Regular array k:     
function - Var i:               12
function - Associative array j: 
function - Regular array k: