Bash

Initialisation section:

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#!/usr/bin/env bash

set -eu -o pipefail

script_directory="$(cd -P "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
project_directory="${script_directory}/.."

Execute command for each line:

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#!/usr/bin/env bash

while read -r line; do
  # skip empty lines
  if [ -z "$line" ]; then
    continue
  fi
  echo "- ${line}"
done < <(find . -type d -name node_modules)

Can be also used with done < input.out

Loop through array items:

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#!/usr/bin/env bash
files=(
  "/etc/passwd"
  "/etc/group"
  "/etc/hosts"
)

for i in "${files[@]}"; do
  echo "- ${i}"
done

named pipes

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#!/usr/bin/env bash

# remove previous named pipe
rm -f pipe || true

# create a named pipe
mknod pipe p

# open a file for reading and writing
# save it's file descriptor to variable $fd
exec {fd}<>pipe

client() {
  local name=$1

  while true; do
    sleep 3
    echo "[client ${name}] hi" >&$fd
  done
}

client one &
client two &
client three &

while read -r -u "$fd" line; do
  echo "[read line] ${line}"
done