Execute bash commands from a Rakefile
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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.
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)
%{echo "World!"} defines a String. I expect you wanted %x{echo "World!"} .
%x{echo "World!"} executes the command and returns the output (stdout). You will not see the result. But you may do:
puts %x{echo "World!"}
There are more ways to call a system command:
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