I have the following Rakefile
desc "Runs tests"
namespace :test do
task :api do
`mocha`
end
end
When I run the command rake test:api, I don't get the nice output of dots that I would if I just ran the command mocha.
How do I print the output of a command real-time in a rake task?
You can just put the output:
puts `mocha`
The backticks ` are calling the command mocha and return the output of the command.
You may also use %x{}:
puts %x{mocha}
Or you use system:
system('mocha')
Or you store the output for later use in a variable:
output = `mocha`
puts output
Related
When a rake task is called via backpacks its output is suppressed:
task :two do
puts 'two'
end
task :one do
puts 'one'
`rake two`
end
-bash> bundle exec rake one
one
Whereas, the output is displayed when called via .invoke:
task :one do
puts 'one'
Rake::Task['two'].invoke
end
-bash> bundle exec rake one
one
two
Why is the output suppressed with backticks, and how can it be displayed?
The above is a contrived example, but ultimately I want to be able to run a local rake task that itself runs a remote rake task, on Heroku, and I want to see its output in real time (because the remote task is interactive, i.e. it asks questions via puts and waits for user/standard input via $stdin.gets.chomp):
task :one do
puts 'one'
`heroku run rake my_app:reset_user_passwords --app #{MY_APP_NAME}`
end
Backticks return the standard output of command so if you want to see the result, just call puts:
task :one do
puts 'one'
puts `heroku run rake my_app:reset_user_passwords --app #{MY_APP_NAME}`
end
If you want a interactive execution, you can try to use IO#expect
I am writing a task in capistrano 3.4 to print git version number in deployed code. I am able to print the code. Here i want to store the output code in some variable. How i can store the output of shell command in ruby variable. below is my task.
desc "version number"
task :set_current_version do
on roles(:app) do
execute "version=#{current_path}/REVISION ; cat $version "
end
end
I need to store the cat $version output in variable. So i can refer this variable in another code.
I got this solved this myself by using capture method below is example.
on '1.example.com' do
if test("[ -f somefile.txt ]")
execute(:cp, 'somefile.txt', 'somewhere_else.txt')
end
ls_output = capture(:ls, '-l')
end
I am building a gem for command line use, and I am aware of the if __FILE__ == $0 method for determining whether the file being run is the current file (from Run code only if script called from the command line), however this doesn't work in my case. I have a module with an initialize function that I would like to run when the gem is called from the command line.
module MyApp
def self.initialize
# do command line stuff
end
def self.test
# run a rake test
end
end
MyApp::initialize
However, when running rake test it calls the initialize function which returns an error:
/Library/WebServer/Documents/myapp ❤ rake test
Options:
-v, --[no-]verbose Run verbosely
-h, --help Show this message
rake aborted!
Command failed with status (255): [ruby -I"lib" -I"/Users/bbriggs/.rvm/gems/ruby-2.0.0-p195/gems/rake-10.1.0/lib" "/Users/bbriggs/.rvm/gems/ruby-2.0.0-p195/gems/rake-10.1.0/lib/rake/rake_test_loader.rb" "test/test_myapp.rb" ]
/Users/bbriggs/.rvm/gems/ruby-2.0.0-p195/bin/ruby_noexec_wrapper:14:in `eval'
/Users/bbriggs/.rvm/gems/ruby-2.0.0-p195/bin/ruby_noexec_wrapper:14:in `<main>'
Tasks: TOP => test
(See full trace by running task with --trace)
I think this is because I am doing MyApp:initialize, because if I take that out of my code the rake test runs as expected, but the command line tool no longer works.
At the moment I am testing my app via bundle exec bin/myapp, and printing out the __FILE__ and $0 variables give me bin/myapp and path/to/lib/myapp.rb respectively, so I was wondering what the best way is to detect whether the module is being required or called directly. Am I even doing this right? I'm a bit of a Ruby newbie. :-)
Finally figured this out. Instead of running MyApp:initialize in lib/myapp.rb I put it in the bin/myapp file. This ensures that it is only run when the app is run from the command line and not when being tested via Rake or required by another script.
Let's say I have some terminal commands like:
sudo mycommand1
mycommand2
#.....
What should I do run them via ruby script (not bash) in Ubuntu?
UPDATE:
I have a ruby script:
def my_method1()
#calculating something.....
end
def method2(var1, var2)
#how do I sudo mycommand1 and any other Lunix command from here?
end
def method3(var4)
#calculating something2....
end
You can do system, exec, or place the command in backticks.
exec("mycommand") will replace the current process so that's really only pratical at the end of your ruby script.
system("mycommand") will create a new process and return true if the command succeeded and nil otherwise.
If you need to use the output of your command in your Ruby script use backticks:
response = 'mycommand`
There are many questions on SO that answer this. However you can run a command in many ways using system, exec, (backticks), %x{} or using open3. I prefer to use open3 -
require 'open3'
log = File.new("#{your_log_dir}/script.log", "w+")
command = "ls -altr ${HOME}"
Open3.popen3(command) do |stdin, stdout, stderr|
log.puts "[OUTPUT]:\n#{stdout.read}\n"
unless (err = stderr.read).empty? then
log.puts "[ERROR]:\n#{err}\n"
end
end
If you want to know more about other options you can refer to Ruby, Difference between exec, system and %x() or Backticks for links to relevant documentation.
You can try these approaches:
%x[command]
Kernel.system"command"
run "command"
make some file.rb with:
#!/path/to/ruby
system %{sudo mycommand1}
system %{mycommand2}
and the chmod the file with exec permissions (e.g. 755)
It you need to pass variables between the two commands, run them together:
system %{sudo mycommand1; \
mycommand2}
I have one simple script:
fork do
STDOUT.reopen(File.open('/tmp/log', 'w+'))
STDOUT.sync = true
exec 'bundle exec ruby script.rb'
end
script.rb:
loop do
sleep 1
puts "MESSAGE"
end
When it work, all outputs is buffering(?) and writes to /tmp/log by big pices.
It works only if I modify script:
$stdout.puts "MESSAGE"
$stdout.flush
How can I do the same without modifying script.rb ?
Thanks.
When you call exec, you create a new process, and although this process inherits the file you set as standard out, it doesn't inherit the other settings, in particular the sync setting.
In order to get unbuffered output in the new process, you need to set it in that process. If you don't want to modify script.rb one workaround could be to create another file, named somethig like sync.rb containing just:
STDOUT.sync = true
which you can then require when running your command:
exec 'bundle exec ruby -r./sync script.rb'
The new Ruby process will now require sync.rb, which simply sets sync mode on STDOUT to true before executing your script.