Note: I'm new to Ruby and so the terminology and/or syntax below may be wrong.
Is there a way to watch STDOUT my ruby process without blocking the rest of my code? Something like:
$stdout.read_lines {|line| // This block is executed on each line logged via `puts`
do_something() if line == 'some interesting string'
}
puts 'Hello world'
puts 'some interesting string' // This would cause the `do_something` line to be executed
I have seen examples where a new process can be created and watched in a similar fashion, but none where the current process's stdout was being watched.
Many thanks.
Edit:
Specifically I am looking to execute some code when this line is executed in my Vagrant setup: https://github.com/cogitatio/vagrant-hostsupdater/blob/master/lib/vagrant-hostsupdater/HostsUpdater.rb#L103
It looks like the message is logged to #ui which I believe is an instance this module https://github.com/hashicorp/vagrant/blob/master/lib/vagrant/ui.rb
Related
I assume this is very newbie stuff but I'm learning Ruby by doing, and I'm developing a small CLI tool that receives a couple of parameters in order to do its stuff properly. This is my current workflow:
I want to test (using Minitest) all the possible flows:
Exits with 0 and help message is shown if ARGV.count != 2
Exits with 1 if first param is not correct
Exits with 1 if second param is not correct
Exits with 1 if both params are not correct
Exits with 0 and does stuff if all params are correct
Now, if I run tests the only thing I see is the help output as there is no parameter being passed.
So, a couple of questions:
How can I pass arguments to the main program in tests?
How can I test the output? (I'm using puts)
Thanks!
nice diagram!
you can either use helpers like aruba https://github.com/cucumber/aruba
or dig into ruby internals in order to bend it to your will!
# test.rb
pseudoIO = StringIO.new
$stdout = pseudoIO
puts "hi #{ARGV.join(', ')}"
ARGV.replace ["file1"]
puts "now its #{ARGV.join(', ')}"
abort "captured: #{pseudoIO.string}"
output should be
ruby text.rb "whutup"
# => captured: hi whutup
# => now its file1
I'm writing some code which takes a file, passes that file to one of several binaries for processing, and monitors the conversion process for errors. I've written and tested the following routine on OSX but linux fails for reasons about which I'm not clear.
#run the command, capture the output so it doesn't display
PTY.spawn(command) {|r,w,pid|
until r.eof? do
##mark
puts r.readline
end
}
The command that runs varies quite a lot and the code at the ##mark has been simplified into a local echo in an attempt to debug the problem. The command executes and the script prints the expected output in the terminal and then throws an exception.
The error it produces on Debian systems is: Errno::EIO (Input/output error - /dev/pts/0):
All of the command strings I can come up with produce that error, and when I run the code without the local echo block it runs just fine:
PTY.spawn(command) {|r,w,pid|}
In either case the command itself executes fine, but it seems like debian linux isn't sending eof up the pty. The doc pages for PTY, and IO on ruby-doc don't seem to lend any aid here.
Any suggestions? Thanks.
-vox-
So I had to go as far as reading the C source for the PTY library to get really satisfied with what is going on here.
The Ruby PTY doc doesn't really say what the comments in the source code say.
My solution was to put together a wrapper method and to call that from my script where needed. I've also boxed into the method waiting on the process to for sure exit and the accessing of the exit status from $?:
# file: lib/safe_pty.rb
require 'pty'
module SafePty
def self.spawn command, &block
PTY.spawn(command) do |r,w,p|
begin
yield r,w,p
rescue Errno::EIO
ensure
Process.wait p
end
end
$?.exitstatus
end
end
This is used basically the same as PTY.spawn:
require 'safe_pty'
exit_status = SafePty.spawn(command) do |r,w,pid|
until r.eof? do
logger.debug r.readline
end
end
#test exit_status for zeroness
I was more than a little frustrated to find out that this is a valid response, as it was completely undocumented on ruby-doc.
It seems valid for Errno::EIO to be raised here (it simply means the child process has finished and closed the stream), so you should expect that and catch it.
For example, see the selected answer in Continuously read from STDOUT of external process in Ruby and http://www.shanison.com/2010/09/11/ptychildexited-exception-and-ptys-exit-status/
BTW, I did some testing. On Ruby 1.8.7 on Ubuntu 10.04, I don't get a error. With Ruby 1.9.3, I do. With JRuby 1.6.4 on Ubuntu in both 1.8 and 1.9 modes, I don't get an error. On OS X, with 1.8.7, 1.9.2 and 1.9.3, I don't get an error. The behavior is obviously dependent on your Ruby version and platform.
As answered here and here, EIO can be avoided by keeping a file descriptor to the pty slave device open in the parent process.
Since PTY.spawn closes the slave file descriptor passed to the child process, a simple workaround is to open a new one. For example:
PTY.spawn("ls") do |r, w, pid|
r2 = File.open(r.path)
while IO.select([r], [], [], 1)
puts r.gets
end
r2.close
end
ruby-doc.org says this since ruby 1.9:
# The result of read operation when pty slave is closed is platform
# dependent.
ret = begin
m.gets # FreeBSD returns nil.
rescue Errno::EIO # GNU/Linux raises EIO.
nil
end
Ok, so now I get this behavior is "normal" on Linux, but that means it's a little tricky to get the output of a PTY. If you do m.read it reads everything and then throws it away and raises Errno::EIO. You really need to read the content chunk by chunk with m.readline. And even then you risk losing the last line if it doesn't end with "\n" for whatever reason. To be extra safe you need to read the content byte by byte with m.read(1)
Additional note about the effect of tty and pty on buffering: it's not the same as STDOUT.sync = true (unbuffered output) in the child process, but rather it triggers line buffering, where output is flushed on "\n"
I'm building a daemon that will help me manage my server(s). Webmin works fine, as does just opening a shell to the server, but I'd prefer to be able to control server operations from a UI I design, and also expose some functionality to end users.
The daemon will pick up actions from a queue and execute them. However, since I'll be accepting input from users, I want to make sure they're not permitted to inject something dangerous into a privileged shell command.
Here's a fragment that exemplifies my problem:
def perform
system "usermod -p #{#options['shadow']} #{#options['username']}"
end
A gist that explains more: https://gist.github.com/773292
I'm not positive if typical escaping and sanitizing of inputs is enough for this case, and being a designer, I don't have a ton of security-related experience. I know that this is something that should probably be obvious to me, but its not!
How can I ensure that the web application that will create and serialize the actions can't pass dangerous text into the privileged process that receives the actions?
Thanks for the help
arb
It doesn't look like you need a shell for what you're doing. See the documentation for system here: http://ruby-doc.org/core/classes/Kernel.html#M001441
You should use the second form of system. Your example above would become:
system 'usermod', '-p', #options['shadow'], #options['username']
A nicer (IMO) way to write this is:
system *%W(usermod -p #{#options['shadow']} #{#options['username']})
The arguments this way are passed directly into the execve call, so you don't have to worry about sneaky shell tricks.
If you need not just the exit status but also the result you probably want to use Open3.popen3:
require 'open3'
stdin, stdout, stderr = Open3.popen3('usermod', '-p', #options['shadow'], #options['username'])
stdout.gets
sterr.gets
More information here: Getting output of system() calls in Ruby
I'd suggest looking into the 'shellwords' module. This script:
require 'shellwords'
parts = ['echo', "'hello world'; !%& some stuff", 'and another argument']
command = Shellwords.shelljoin( parts )
puts command
output = `#{ command }`
puts output
outputs the escaped text and the expected output:
echo \'hello\ world\'\;\ \!\%\&\ some\ stuff and\ another\ argument
'hello world'; !%& some stuff and another argument
This is an old question, but since it's pretty much the only real answer you'll find when googling I thought I'd add a caveat. The multi argument version of system seems reasonably safe on Linux, but it is NOT on Windows.
Try system "dir", "&", "echo", "hi!"
on a Windows system. Both dir and echo will be run. Echo could of course just as well be something far less innocuous.
I know this is an old thread, but there is another option that was lightly touched on by Simon Hürlimann.
There is not a lot of information about this topic and I think this might help others in need.
For this example we'll use Open3 which gives you the ability to run commands synchronously or asynchronously, and provides stdout, stderr, exit codes, and PID.
Open3 grants you access to stdout, stderr, exit codes and a thread to wait for the child process when running another program. You can specify various attributes, redirections, current directory, etc., of the program in the same way as for Process.spawn. (Source: Open3 Docs)
I chose to format the output as a CommandStatus object. This contains our stdout, stderr, pid (Of the worker thread) and exitstatus.
class Command
require 'open3'
class CommandStatus
#stdout = nil
#stderr = nil
#pid = nil
#exitstatus = nil
def initialize(stdout, stderr, process)
#stdout = stdout
#stderr = stderr
#pid = process.pid
#exitstatus = process.exitstatus
end
def stdout
#stdout
end
def stderr
#stderr
end
def exit_status
#exitstatus
end
def pid
#pid
end
end
def self.execute(command)
command_stdout = nil
command_stderr = nil
process = Open3.popen3(ENV, command + ';') do |stdin, stdout, stderr, thread|
stdin.close
stdout_buffer = stdout.read
stderr_buffer = stderr.read
command_stdout = stdout_buffer if stdout_buffer.length > 0
command_stderr = stderr_buffer if stderr_buffer.length > 0
thread.value # Wait for Process::Status object to be returned
end
return CommandStatus.new(command_stdout, command_stderr, process)
end
end
cmd = Command::execute("echo {1..10}")
puts "STDOUT: #{cmd.stdout}"
puts "STDERR: #{cmd.stderr}"
puts "EXIT: #{cmd.exit_status}"
While reading the STDOUT/ERR buffers, I use command_stdout = stdout_buffer if stdout_buffer.length > 0 to control whether the command_stdout variable is assigned or not. You should pass nil instead of "" when no data is present. It's more clear when handing data later on.
You probably noticed me using command + ';'. The reason for this is based on the documentation from Kernel.exec (Which is what popen3 uses):
If the string from the first form (exec("command")) follows these
simple rules:
no meta characters
no shell reserved word and no special built-in
Ruby invokes the command directly without shell
You can force shell invocation by adding ";" to the string (because
";" is a meta character)
This simply prevents a Ruby from throwing a 'spawn': No such file or directory error if you pass a malformed command. Instead it will pass it straight to the kernel where the error will be resolved gracefully and appear as STDERR instead of an uncaught exception.
Modern, secure and simple solution (popen will escape arguments for you):
IO.popen(['usermod', '-p', #options['shadow'], #options['username']]).read
(#read will close the IO before returning)
I'm looking to expose an interactive command line program via JSON or another RPC style service using Ruby. I've found a couple tricks to do this, but im missing something when redirecting the output and input.
One method at least on linux is to redirect the stdin and stdout to a file then read and write to that file asynchronously with file reads and writes. Another method ive been trying after googling around was to use open4. Here is the code I wrote so far, but its getting stuck after reading a few lines from standard output.
require "open4"
include Open4
status = popen4("./srcds_run -console -game tf +map ctf_2fort -maxplayers 6") do |pid, stdin, stdout, stderr|
puts "PID #{pid}"
lines=""
while (line=stdout.gets)
lines+=line
puts line
end
while (line=stderr.gets)
lines+=line
puts line
end
end
Any help on this or some insight would be appreciated!
What I would recommend is using Xinetd (or similar) to run the command on some socket and then using the ruby network code. One of the problems you've already run into in your code here is that your two while loops are sequential, which can cause problems.
Another trick you might try is to re-direct stderr to stdout in your command, so that your program only has to read the stdout. Something like this:
popen4("./srcds_run -console -game tf +map ctf_2fort -maxplayers 6 2>&1")
The other benefit of this is that you get all the messages/errors in the order they happen during the program run.
EDIT
Your should consider integrating with AnyTerm. You can then either expose AnyTerm directly e.g. via Apache mod_proxy, or have your Rails controller act as the reverse proxy (handling authentication/session validation, then playing back controller.request minus any cookies to localhost:<AnyTerm-daemon-port>, and sending back as a response whatever AnyTerm replies with.)
class ConsoleController < ApplicationController
# AnyTerm speaks via HTTP POST only
def update
# validate session
...
# forward request to AnyTerm
response = Net::HTTP.post_form(URI.parse('http://localhost:#{AnyTermPort}/', request.params))
headers['Content-Type'] = response['Content-Type']
render_text response.body, response.status
end
Otherwise, you'd need to use IO::Select or IO::read_noblock to know when data is available to be read (from either network or subprocess) so you don't deadlock. See this too. Also check that either your Rails is used in a multi-threaded environment or that your Ruby version is not affected by this IO::Select bug.
You can start with something along these lines:
status = POpen4::popen4("ping localhost") do |stdout, stderr, stdin, pid|
puts "PID #{pid}"
# our buffers
stdout_lines=""
stderr_lines=""
begin
loop do
# check whether stdout, stderr or both are
# ready to be read from without blocking
IO.select([stdout,stderr]).flatten.compact.each { |io|
# stdout, if ready, goes to stdout_lines
stdout_lines += io.readpartial(1024) if io.fileno == stdout.fileno
# stderr, if ready, goes to stdout_lines
stderr_lines += io.readpartial(1024) if io.fileno == stderr.fileno
}
break if stdout.closed? && stderr.closed?
# if we acumulated any complete lines (\n-terminated)
# in either stdout/err_lines, output them now
stdout_lines.sub!(/.*\n/m) { puts $& ; '' }
stderr_lines.sub!(/.*\n/m) { puts $& ; '' }
end
rescue EOFError
puts "Done"
end
end
To also handle stdin, change to:
IO.select([stdout,stderr],[stdin]).flatten.compact.each { |io|
# program ready to get stdin? do we have anything for it?
if io.fileno == stdin.fileno && <got data from client?>
<write a small chunk from client to stdin>
end
# stdout, if ready, goes to stdout_lines
I am using rspec for my test in a ruby project, and I want to spec that my program should not output anything when the -q option is used. I tried:
Kernel.should_not_receive :puts
That did not result in a failed test when there was output to the console.
How do I verify the absents of text output?
puts uses $stdout internally. Due to the way it works, the easiest way to check is to simply use: $stdout.should_not_receive(:write)
Which checks nothing is written to stdout as expected.
Kernel.puts (as above) would only result in a failed test when it
is explictely called as such (e.g. Kernel.puts "Some text"), where
as most cases it's call in the scope of the current object.
The accepted answer above is incorrect. It "works" because it doesn't receive a :write message but it might have received a :puts message.
The correct line should read:
$stdout.should_not_receive(:puts)
Also you need to make sure you put the line before the code that will write to STDIO. For instance:
it "should print a copyright message" do
$stdout.should_receive(:puts).with(/copyright/i)
app = ApplicationController.new(%w[project_name])
end
it "should not print an error message" do
$stdout.should_not_receive(:puts).with(/error/i)
app = ApplicationController.new(%w[project_name])
end
That's an actual working RSpec from a project