retry.sh

#!/bin/bash

# The MIT License (MIT) 
# Copyright (c) 2022-present Nathan Todd-Stone 
# https://en.wikipedia.org/wiki/MIT_License#License_terms

# define the retry fn
retry() {
    e=0
    if [[ $- =~ e ]]; then
        e=1
    fi
    set +e
    max_tries=10
    sleep_seconds=3
    for i in $(seq 1 $max_tries); do
        ("$@")
        if [ $? = 0 ]; then
            break
        else
            echo retrying: "$@" 1>&2
            sleep $sleep_seconds 1>&2
        fi
        if [ $i = $max_tries ]; then
            echo all retries failed 1>&2
            exit 1
        fi
    done
    if [ e = 1 ]; then
        set -e
    fi
}

# export it so its available in subprocesses
export -f retry

fn() {
    set -eou pipefail
    # false # to trigger retries
    echo process $1
}

# export it so its available in subprocesses
export -f fn

inputs="
a
b
c
"

# run the fn in parallel over the inputs, retrying failures
echo "$inputs" | xargs -n1 -P$(nproc) -I{} bash -c "retry fn {}"