wait_group_ex

#!/bin/bash
#
# Example similar to the one in Go documentation
# (https://pkg.go.dev/sync#example-WaitGroup).

readonly DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
. ${DIR}/../gobash


function main() {
        # This function illustrates how we create and use
        # WaitGroup. However, this example does not really need
        # WaitGroup as we wait for all sub processes; we can simply
        # use wait command at the end of the function to wait for
        # every process that we spawned. The value of this example is to
        # illustrate how to create a WaitGroup, processes to
        # it, and wait (which would be a nice approach if one has to
        # wait only for a subset of processes).

        local -r wg=$(WaitGroup)

        # If values are needed only locally (not passing/returning
        # to/from functions/processes), we use array structure
        # available in bash.
        local -r urls=(
                "http://www.golang.org/"
                "http://www.google.com/"
                "http://www.example.com/"
        )

        local url
        for url in ${urls[@]}; do
                ( curl "${url}" 2>&1 ) &

                # Just like the wait command, it is only legal to wait
                # for sub processes (i.e., you should not be adding
                # random values to a WaitGroup).
                $wg add $!
        done
        $wg wait
}

main