create an array from original array but basis on where code is running? - linux

Question

I have three machine (each in different datacenter) in a machines array.
If my shell script is running on abc datacenter then I want to scp files from machineA.abc.host.com which will be my local box. I will pick other two boxes as remote servers to copy files incase local box is down.
If my shell script is running on def datacenter then I want to scp files from machineB.def.host.com which will be my local box. I will pick other two boxes as remote servers to copy files incase local box is down.
If my shell script is running on pqr datacenter then I want to scp files from machineC.pqr.host.com which will be my local box. I will pick other two boxes as remote servers to copy files incase local box is down.
Below is my script but I believe it can be done in much better way instead of using three different variables and then having three scp staetments seprated by or:
machines=(machineA.abc.host machineB.def.host.com machineC.pqr.host.com)
case $(hostname -f) in
*abc.host.com)
local_server=("${machines[0]}")
primary_remote==("${machines[1]}")
secondary_remote==("${machines[2]}")
;;
*def.host.com)
local_server=("${machines[1]}")
primary_remote==("${machines[2]}")
secondary_remote==("${machines[0]}")
;;
*pqr.host.com)
local_server=("${machines[2]}")
primary_remote==("${machines[0]}")
secondary_remote==("${machines[1]}")
;;
*) echo "unknown host: $(hostname -f), exiting." >&2 && exit 1 ;;
# ?
esac
export local="$local_server"
export remote1="$primary_remote"
export remote2="$secondary_remote"
copyFiles() {
el=$1
primsec=$2
# can we just iterate from for loop instead of writing three scp statements?
(scp -C -o StrictHostKeyChecking=no goldy#"$local":/proc/data/abc_187_"$el"_111_8.data "$primsec"/.) || (scp -C -o StrictHostKeyChecking=no goldy#"$remote1":/proc/data/abc_187_"$el"_111_8.data "$primsec"/.) || (scp -C -o StrictHostKeyChecking=no goldy#"$remote2":/proc/data/abc_187_"$el"_111_8.data "$primsec"/.)
}
export -f copyFiles
# using gnu parallel here to call above methods parallely
Now as you can see I have three scp statements one for local box, other for remote1 and remote2. What I am thinking is maybe we can get rid of these three scp statements and instead store hostnames (in a particular order, first index can be local box and other two can be remote) in an array and then iterate that array from a for loop and just write one scp statement?
for p in "$machines"; do scp -C -o StrictHostKeyChecking=no goldy#"$p":/proc/data/abc_187_"$el"_111_8.data "$primsec"/. && break; done > /dev/null 2>&1
If this is possible then how can I reshuffle machines array accordingly or maybe create a different array then with right machine in them at proper index?
Update:
Somehow my for loop inside that function is not running at all:
copyFiles() {
local el=$1
local primsec=$2
local remote_file="/proc/data/abc_187_${el}_111_8.data"
for host in "${hosts[#]}"; do
echo "$host"
echo "scp -C -o StrictHostKeyChecking=no "goldy#$host:$remote_file" "$primsec"/." && break
done
}
export hosts
export -f copyFiles
parallel -j 5 copyFiles {} $proc::: ${pro[#]} &
parallel -j 5 copyFiles {} $data::: ${seco[#]} &
wait
echo "everything copied"

Answer 1

How about this: it uses
an associative array to hold the "local" machine names
an array to hold the sequence of hosts for scp
a for loop to iterate over the possible hosts, and break after the first successful scp
#!/bin/bash
declare -A machines=(
[abc]=machineA.abc.host.com
[def]=machineB.def.host.com
[pqr]=machineC.pqr.host.com
)
IFS=. read -a host_parts < <(hostname -f)
case "${host_parts[1]}" in
abc) hosts=( "${machines[abc]}" "${machines[def]}" "${machines[pqr]}" ) ;;
def) hosts=( "${machines[def]}" "${machines[pqr]}" "${machines[abc]}" ) ;;
pqr) hosts=( "${machines[pqr]}" "${machines[abc]}" "${machines[def]}" ) ;;
*) echo "unknown host: $(hostname -f), exiting." >&2; exit 1 ;;
esac
copyFiles() {
local el=$1
local primsec=$2
local remote_file="/proc/data/abc_187_${el}_111_8.data"
for host in "${hosts[#]}"; do
scp -C -o StrictHostKeyChecking=no "goldy#$host:$remote_file" "$primsec"/. && break
done
}
export hosts
export -f copyFiles