functional.sh

#!/bin/bash

function silent() {
  "$@" >/dev/null 2>&1
}

function command_exists() {
  silent hash "$@"
}

function not() {
  ! "$@"
}

function map() {
  declare -a basecmd cmd
  declare -i substitution=0

  basecmd=("$@")
  # TODO: make xargs or parallel work with funcs like `silent` :|
  # if command_exists parallel; then
  #   parallel --keep-order "${basecmd[@]}"
  # elif command_exists xargs; then
  #   # TODO: detect FreeBSD parallel option
  #   xargs -I{} "${basecmd[@]}"
  # else
    if [[ "${cmd[*]}" == "*{}*" ]]; then
      substitution=1
    fi

    while read line; do
      if [ $substitution = 1 ]; then
        cmd=("${basecmd[@]//{}/$line}")
      else
        cmd=("${basecmd[@]}" $line)
      fi
      "${cmd[@]}" && echo "$line"
    done
  # fi
}

function filter() {
  map silent "$@"
}

$ echo -e "google.com\nyahoo.com\nbaddomain------------llkjlkj.com" | filter host
google.com
yahoo.com
$ echo -e "google.com\nyahoo.com\nbaddomain------------llkjlkj.com" | filter not host
baddomain------------llkjlkj.com