Converting a loop of code to function

Question

I want to retry a command for 5 times with an interval of 20 seconds. I want this command to be passed as a method parameter. How to do it? And once the function is written how to pass the value to the function?

I want my current code to be converted to a function which takes a set of parameters. How to write and call this function in my shell script?

My current code is like this :

  trialNumber=0
    until [ $trialNumber -ge 5]  
     do
        ssh $USERID@$HOST $SCRIPT_LOCATION/runme.sh   # This line is my command and it may very with number of parameters or command itself.
       [ $? -eq 0 ] && break
      trialNumber=$[$trialNumber+1]
      sleep 20
   done

( Above code is embedded at many places I want to move it into a function).

Answer 1

retry() {
  trialNumber=$1 delay=$2; shift 2
  while [ "$trialNumber" -gt 0 ]; do
    "$@" && return
    ret=$?
    sleep "$delay"
    trialNumber=$(($trialNumber - 1))
  done
  return "$ret"
}

retry 5 20 ssh "$USERID@$HOST" "$SCRIPT_LOCATION/runme.sh"

Though the last sleep in case of failure is not necessary. May be better as:

retry() {
  trialNumber=$1 delay=$2; shift 2
  until "$@"; do
    ret=$?
    trialNumber=$(($trialNumber - 1))
    [ "$trialNumber" -gt 0 ] || return "$ret"
    sleep "$delay"
  done
}

Answer 2

Use the retry command.

~$ retry --times 5 --delay 20 -- ssh $USERID@$HOST $SCRIPT_LOCATION/runme.sh

https://github.com/minfrin/retry

Available out the box in recent Debian, Ubuntu, and Nix.