Multi-threaded ping script

Question

I have this

#! /bin/bash

cd ~
hostname=`hostname`
cat /opt/ip.txt | while read line;
do
# do something with $line here
RES=`ping -c 2 -q $line |  grep "packet loss"`

echo "---" >> /opt/os-$hostname.txt
echo "---" 
echo "$line $RES" >> /opt/os-$hostname.txt
echo "$line $RES" 
done

How I can make the script multi-threaded? I would like to speed up the performance.

Answer 1

You can use the <(...) notation for starting a subprocess and then cat all the outputs together:

myping() {
  ping -c 2 -q "$1" | grep "packet loss"
}

cat <(myping hostname1) <(myping hostname2) ...

To use a loop for this, you will need to build the command first:

cat /opt/ip.txt | {
  command='cat'
  while read line
  do
    command="$command "'<'"(myping $line)"
  done
  eval "$command"
}

If you really want the delimiting --- of your original, I propose to add an echo "---" in the myping.

If you want to append the output to a file as well, use tee:

  eval "$command" | tee -a /opt/os-$hostname.txt