require "process"

# For our example we'll exec `ls`. Crystal requires the
# full path to the binary we want to execute, so we'll use
# `Process.find_executable` to find it (probably `/bin/ls`).
binary = Process.find_executable("ls")
if binary.nil?
  raise "Could not find 'ls' executable"
end

# `exec` requires arguments in array form (as opposed to
# one big string). We'll give `ls` a few common arguments.
# Note that the first argument should be the program name.
args = ["ls", "-a", "-l", "-h"]

# `exec` also needs a set of environment variables to use.
# Here we just provide our current environment.
env = ENV.to_h

# Here's the actual `Process.exec` call. If this call is
# successful, the execution of our process will end here
# and be replaced by the `/bin/ls -a -l -h` process.
# If there is an error, an exception will be raised.
Process.exec(binary, args, env)