When I use mapfile with parallel to create an array inside a function the array isn't created properly.
Why is this?
mapfile -t arr < <(parallel -j 0 echo ::: {1..5})
declare -p arr
declare -a arr=([0]="1" [1]="2" [2]="3" [3]="4" [4]="5")
mapRay() { mapfile -t "$1" < <(parallel -j 0 "$2" ::: "$3"); }
mapRay arr echo {1..2}
declare -p arr
declare -a arr=([0]="1")
Why is this?
$ cat un714227.sh
mapRay(){ mapfile -t "$1" < <(parallel -j 0 "$2" ::: "$3"); }
mapRay arr echo {1..2}
$ bash -x ./un714227.sh
++ mapRay arr echo 1 2
++ mapfile -t arr
+++ parallel -j 0 echo ::: 1
As you see, mapRay is invoked with $1=arr $2=echo $3=1 $4=2 and parallel -j0 "$2" ::: "$3" runs echo with argument 1 only, ignoring the 2.
The array correctly contains the output of the parallel command; it is the input to the parallel command that wasn't what you apparently wanted.
You probably want something like "${@:3}" to get all arguments after the first 2.
Alternatively, a classic way to handle special (sometimes optional) then homogenous but varying args is to handle the special args and shift them out, then handle the rest:
mapRay(){
local var="$1" cmd="$2"
shift 2
mapfile -t "$var" < <(parallel -j0 "$cmd" ::: "$@")
}
$@, thanks a lot, I tried using set -x but it didn’t show anything, thanks for -x as well
set -x‘and x do the same thing I must just have not seen it when I used set -x to the guy who made the edit saying ‘that’s specific to bash not sh’ well this is a bash question not a sh question so there was no need in that
sh well this is a bash question not a sh question so there was no need in that
sh question, bash syntax should be used and this should be obvious as mapfile is a bash thing
Please have a look at parset (https://www.gnu.org/software/parallel/parset.html)
parset myarray seq 3 ::: 4 5 6
echo "${myarray[1]}"
Or in your case:
parset arr -j0 echo ::: {1..2}
echo "${arr[1]}"
It will also handle if the output from each job is multiple lines.
parallel version, my one automatically echos the input, what’s the advantage to parset? does it create an array? so would eliminate the need for me using mapfile?
parset allows you to create an array from the function and inputs you give it, many thanks, I’ll be using this now.