Run the command, writing the command's standard out and standard error
to stdout
and stderr
, and saving its exit status
object to status
returns self
; stdout
, stderr
,
status
, and exitstatus
will be populated with
results of the command
Errno::EACCES when you are not privileged to execute the command
Errno::ENOENT when the command is not available on the system (or not in the current $PATH)
Chef::Exceptions::CommandTimeout when the command does not complete within
timeout
seconds (default: 600s)
# File lib/mixlib/shellout/unix.rb, line 39 def run_command @child_pid = fork_subprocess configure_parent_process_file_descriptors # Ruby 1.8.7 and 1.8.6 from mid 2009 try to allocate objects during GC # when calling IO.select and IO#read. Some OS Vendors are not interested # in updating their ruby packages (Apple, *cough*) and we *have to* # make it work. So I give you this epic hack: GC.disable # CHEF-3390: Marshall.load on Ruby < 1.8.7p369 also has a GC bug related # to Marshall.load, so try disabling GC first. propagate_pre_exec_failure @result = nil @execution_time = 0 write_to_child_stdin until @status ready = IO.select(open_pipes, nil, nil, READ_WAIT_TIME) unless ready @execution_time += READ_WAIT_TIME if @execution_time >= timeout && !@result raise CommandTimeout, "command timed out:\n#{format_for_exception}" end end if ready && ready.first.include?(child_stdout) read_stdout_to_buffer end if ready && ready.first.include?(child_stderr) read_stderr_to_buffer end unless @status # make one more pass to get the last of the output after the # child process dies if results = Process.waitpid2(@child_pid, Process::WNOHANG) @status = results.last redo end end end self rescue Exception # do our best to kill zombies Process.waitpid2(@child_pid, Process::WNOHANG) rescue nil raise ensure # no matter what happens, turn the GC back on, and hope whatever busted # version of ruby we're on doesn't allocate some objects during the next # GC run. GC.enable close_all_pipes end
Option validation that is unix specific
# File lib/mixlib/shellout/unix.rb, line 24 def validate_options(opts) # No options to validate, raise exceptions here if needed end
# File lib/mixlib/shellout/unix.rb, line 144 def child_process_status @process_status_pipe[0] end
# File lib/mixlib/shellout/unix.rb, line 140 def child_stderr @stderr_pipe[0] end
# File lib/mixlib/shellout/unix.rb, line 132 def child_stdin @stdin_pipe[1] end
# File lib/mixlib/shellout/unix.rb, line 136 def child_stdout @stdout_pipe[0] end
When a new process is started with chef, it shares the file descriptors of the parent. We clean the file descriptors coming from the parent to prevent unintended locking if parent is killed. NOTE: After some discussions we've decided to iterate on file descriptors upto 256. We believe this is a reasonable upper limit in a chef environment. If we have issues in the future this number could be made to be configurable or updated based on the ulimit based on platform.
# File lib/mixlib/shellout/unix.rb, line 190 def clean_parent_file_descriptors # Don't clean $stdin, $stdout, $stderr, process_status_pipe. 3.upto(256) do |n| # We are checking the fd for error pipe before attempting to # create a file because error pipe will auto close when we # try to create a file since it's set to CLOEXEC. if n != @process_status_pipe.last.to_i begin fd = File.for_fd(n) fd.close if fd rescue end end end end
# File lib/mixlib/shellout/unix.rb, line 148 def close_all_pipes child_stdin.close unless child_stdin.closed? child_stdout.close unless child_stdout.closed? child_stderr.close unless child_stderr.closed? child_process_status.close unless child_process_status.closed? end
# File lib/mixlib/shellout/unix.rb, line 206 def configure_parent_process_file_descriptors # Close the sides of the pipes we don't care about stdin_pipe.first.close stdin_pipe.last.close unless input stdout_pipe.last.close stderr_pipe.last.close process_status_pipe.last.close # Get output as it happens rather than buffered child_stdin.sync = true if input child_stdout.sync = true child_stderr.sync = true true end
Replace stdout, and stderr with pipes to the parent, and close the reader side of the error marshaling side channel.
If there is no input, close STDIN so when we exec, the new program will know it's never getting input ever.
# File lib/mixlib/shellout/unix.rb, line 160 def configure_subprocess_file_descriptors process_status_pipe.first.close # HACK: for some reason, just STDIN.close isn't good enough when running # under ruby 1.9.2, so make it good enough: stdin_pipe.last.close STDIN.reopen stdin_pipe.first stdin_pipe.first.close unless input stdout_pipe.first.close STDOUT.reopen stdout_pipe.last stdout_pipe.last.close stderr_pipe.first.close STDERR.reopen stderr_pipe.last stderr_pipe.last.close STDOUT.sync = STDERR.sync = true STDIN.sync = true if input end
# File lib/mixlib/shellout/unix.rb, line 253 def fork_subprocess initialize_ipc fork do configure_subprocess_file_descriptors clean_parent_file_descriptors set_group set_user set_environment set_umask set_cwd begin command.kind_of?(Array) ? exec(*command) : exec(command) raise 'forty-two' # Should never get here rescue Exception => e Marshal.dump(e, process_status_pipe.last) process_status_pipe.last.flush end process_status_pipe.last.close unless (process_status_pipe.last.closed?) exit! end end
# File lib/mixlib/shellout/unix.rb, line 127 def initialize_ipc @stdin_pipe, @stdout_pipe, @stderr_pipe, @process_status_pipe = IO.pipe, IO.pipe, IO.pipe, IO.pipe @process_status_pipe.last.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC) end
Some patch levels of ruby in wide use (in particular the ruby 1.8.6 on OSX) segfault when you IO.select a pipe that's reached eof. Weak sauce.
# File lib/mixlib/shellout/unix.rb, line 223 def open_pipes @open_pipes ||= [child_stdout, child_stderr] end
Attempt to get a Marshaled error from the side-channel. If it's there, un-marshal it and raise. If it's not there, assume everything went well.
# File lib/mixlib/shellout/unix.rb, line 283 def propagate_pre_exec_failure begin e = Marshal.load child_process_status raise(Exception === e ? e : "unknown failure: #{e.inspect}") rescue EOFError # If we get an EOF error, then the exec was successful true ensure child_process_status.close end end
# File lib/mixlib/shellout/unix.rb, line 244 def read_stderr_to_buffer while chunk = child_stderr.read_nonblock(READ_SIZE) @stderr << chunk end rescue Errno::EAGAIN rescue EOFError open_pipes.delete(child_stderr) end
# File lib/mixlib/shellout/unix.rb, line 234 def read_stdout_to_buffer while chunk = child_stdout.read_nonblock(READ_SIZE) @stdout << chunk @live_stream << chunk if @live_stream end rescue Errno::EAGAIN rescue EOFError open_pipes.delete(child_stdout) end
# File lib/mixlib/shellout/unix.rb, line 123 def set_cwd Dir.chdir(cwd) if cwd end
# File lib/mixlib/shellout/unix.rb, line 113 def set_environment environment.each do |env_var,value| ENV[env_var] = value end end
# File lib/mixlib/shellout/unix.rb, line 106 def set_group if group Process.egid = gid Process.gid = gid end end
# File lib/mixlib/shellout/unix.rb, line 119 def set_umask File.umask(umask) if umask end
# File lib/mixlib/shellout/unix.rb, line 99 def set_user if user Process.euid = uid Process.uid = uid end end
Keep this unbuffered for now
# File lib/mixlib/shellout/unix.rb, line 228 def write_to_child_stdin return unless input child_stdin << input child_stdin.close # Kick things off end