Shell/Bash + expect script based on input list - bash

Question

I'm trying to run a shell script that execute an expect script based on an input list (IP Addresses), but in parallel.
Unfortunately I didn't understood how to achieve it, below my working script that execute the expect script sequentially on each IP contained in the list.
#!/bin/bash
HOST="$1"
USER="user"
PASS="password"
OUT="checkversion.csv"
rm -rf $OUT
touch $OUT
NOW=$(date +"%Y-%m-%d_%H-%M-%S")
echo "Script started at $NOW"
for i in `cat $1`
do
SCRIPT=$(expect -c "
spawn ssh -o HostKeyAlgorithms=+ssh-dss -o KexAlgorithms=+diffie-hellman-group1-sha1 -o StrictHostKeyChecking=no -c 3des-cbc -c aes128-cbc -c aes192-cbc -c aes256-cbc -c aes128-ctr -c aes192-ctr -c aes256-ctr $USER#$i
match_max 100000
expect \"*?assword:*\"
send -- \"$PASS\r\"
expect \"*>*\"
send -- \"start shell\"
send -- \"\r\"
expect \"*%*\"
send -- \"exit\"
send -- \"\r\"
expect \"*>*\"
send -- \"exit\"
send -- \"\r\"
")
VERSION=`echo "$SCRIPT" | grep JUNOS | grep -v WARNING | grep -v possible | grep -v recover`
echo "$i;$VERSION" >> $OUT
done
NOW=$(date +"%Y-%m-%d_%H-%M-%S")
echo "script finished at $NOW - note any errors above"
Could you please help me in found a method to run it in parallel and speedup the process?
Thanks

Answer 1

Please try changing your script as follow:
#!/bin/bash
HOST="$1"
USER="user"
PASS="password"
OUT="checkversion.csv"
rm -rf $OUT
touch $OUT
NOW=$(date +"%Y-%m-%d_%H-%M-%S")
echo "Script started at $NOW"
function runSSH {
PARAM=$1
SCRIPT=$(expect -c "
spawn ssh -o HostKeyAlgorithms=+ssh-dss -o KexAlgorithms=+diffie-hellman-group1-sha1 -o StrictHostKeyChecking=no -c 3des-cbc -c aes128-cbc -c aes192-cbc -c aes256-cbc -c aes128-ctr -c aes192-ctr -c aes256-ctr $USER#$PARAM
match_max 100000
expect \"*?assword:*\"
send -- \"$PASS\r\"
expect \"*>*\"
send -- \"start shell\"
send -- \"\r\"
expect \"*%*\"
send -- \"exit\"
send -- \"\r\"
expect \"*>*\"
send -- \"exit\"
send -- \"\r\"
")
VERSION=`echo "$SCRIPT" | grep JUNOS | grep -v WARNING | grep -v possible | grep -v recover`
echo "$PARAM;$VERSION" >> $OUT
}
for i in `cat $1`; do
# Run SSH in background
runSSH $i &
done
# Wait for background processes to finish...
wait
NOW=$(date +"%Y-%m-%d_%H-%M-%S")
echo "script finished at $NOW - note any errors above"