Execute bash commands from a Rakefile

I would like to execute a number of bash commands from a Rakefile.

I have tried the following in my Rakefile

task :hello do
  %{echo "World!"}
end

but upon executing rake hello there is no output? How do I execute bash commands from a Rakefile?

NOTE:This is not a duplicate as it's specifically asking how to execute bash commands from a Rakefile.

Solution 1:

I think the way rake wants this to happen is with: http://rubydoc.info/gems/rake/FileUtils#sh-instance_method Example:

task :test do
  sh "ls"
end

The built-in rake function sh takes care of the return value of the command (the task fails if the command has a return value other than 0) and in addition it also outputs the commands output.

Solution 2:

There are several ways to execute shell commands in ruby. A simple one (and probably the most common) is to use backticks:

task :hello do
  `echo "World!"`
end

Backticks have a nice effect where the standard output of the shell command becomes the return value. So, for example, you can get the output of ls by doing

shell_dir_listing = `ls`

But there are many other ways to call shell commands and they all have benefits/drawbacks and work differently. This article explains the choices in detail, but here's a quick summary possibilities:

• stdout = %x{cmd} - Alternate syntax for backticks, behind the scenes it's doing the same thing

• exec(cmd) - Completely replace the running process with a new cmd process

• success = system(cmd) - Run a subprocess and return true/false on success/failure (based on cmd exit status)

• IO#popen(cmd) { |io| } - Run a subprocess and connect stdout and stderr to io

• stdin, stdout, stderr = Open3.popen3(cmd) - Run a subprocess and connect to all pipes (in, out, err)