pastel.rb

#!/usr/bin/env ruby
#
# Launch pastel commands using GST syntax.
#
# Example
#
#   $ pastel random ! mix green ! lighten 0.2 ! format
#
# https://github.com/sharkdp/pastel is expected to be in
# /usr/local/bin/pastel. Change the PROGRAM constant if
# you want something else.

SEPARATOR = "!"
PROGRAM = "/usr/local/bin/pastel"

Command = Struct.new(:args, :stdin)

if not ARGV.include?(SEPARATOR)
  # Just execute pastel if we don't have multiple commands
  exec(PROGRAM, *ARGV)
end

argv = ARGV
commands = []

loop do
  sep_idx = argv.index(SEPARATOR)
  if sep_idx
    commands << Command.new(argv.take(sep_idx))
    argv = argv.drop(sep_idx+1)
  else
    commands << Command.new(argv)
    break
  end
end

pids = commands.zip(commands.drop(1)).map do |cmd, next_cmd|
  stdout = nil
  if not next_cmd.nil?
    r, w = IO.pipe
    stdout = w
    next_cmd.stdin = r
  end

  pid = fork do
    STDOUT.reopen(stdout) if stdout
    STDIN.reopen(cmd.stdin) if cmd.stdin
    exec(PROGRAM, *cmd.args)
  end

  cmd.stdin&.close
  stdout&.close

  pid
end


# Execute them
exitstatus = 0
pids.each do |pid|
  Process.waitpid(pid)
  if not $?.success?
    exitstatus = $?.exitstatus
  end
end

exit(exitstatus)