Functional programming with bash experiment.

stream.sh

#!/bin/bash

function stdout {
  echo -e "\e[32m$@\e[0m";
}

function stderr {
  echo -e "\e[31m$@\e[0m" 1>&2;
}

function stdlog {
  echo "$@";
} >> /tmp/foo.log

function :pipe {
  if [ $# -ne 0 ]; then
    :multi $@;
  else
    while read -r; do
      echo $REPLY;
    done
  fi
}

function :multi {
  while read -r; do
    for i in ${@:1}; do
      $i $REPLY;
    done
  done
}

function :eval {
  while read -r; do
    STDIN=$REPLY;
    eval $1;
  done
}

function :color {
  case "$1" in
    'red'     ) :eval 'echo -e "\e[31m$STDIN\e[0m"';;
    'green'   ) :eval 'echo -e "\e[32m$STDIN\e[0m"';;
    'yellow'  ) :eval 'echo -e "\e[33m$STDIN\e[0m"';;
    'blue'    ) :eval 'echo -e "\e[34m$STDIN\e[0m"';;
    'purple'  ) :eval 'echo -e "\e[35m$STDIN\e[0m"';;
    'magenta' ) :eval 'echo -e "\e[36m$STDIN\e[0m"';;
    'grey'    ) :eval 'echo -e "\e[37m$STDIN\e[0m"';;
    *         ) :eval 'echo "$STDIN"';;
  esac
}

#!/bin/bash
source $PWD/stream.sh;

# Create some streams
function a { echo "[ STREAM A ] $@"; }
function b { echo "[ STREAM B ] $@"; }

# Pipe all the things in to the other things
ls -la |:color 'blue' |\
  sed "s/$(whoami)/batman/g" |\
    :eval 'echo "LAYER 1: $STDIN"' |:color 'magenta' |\
      :eval 'echo "LAYER 2: $STDIN"' |:color 'green' |\
        :pipe a b |:color 'yellow';

# Redirect stdout

       ┌─2> stderr 2>
stdin ─┤                    ┌─2> stderr
       └─1> stdout | stdin ─┤
                            └─1> stdout

# Redirect stderr to stdout

       ┌─2> stderr 2>─┐               ┌─2> stderr
stdin ─┤              ├─2>&1 | stdin ─┤      
       └─1> stdout 1>─┘               └─1> stdout

# Redirect stdout

       ┌─2> stderr 2>
stdin ─┤                    ┌─2> stderr
       └─1> stdout | stdin ─┤
                            └─1> stdout

# Redirect stderr to stdout

       ┌─2> stderr 2>&1 ─╖
stdin ─┤                 ║                    ┌─2> stderr      
       └─1> stdout ──────╨─1> stdout | stdin ─┤
                                              └─1> stdout

what have you done