Class: Subprocess::Process
- Inherits:
-
Object
- Object
- Subprocess::Process
- Defined in:
- lib/subprocess.rb
Overview
A child process. The preferred way of spawning a subprocess is through the functions on Subprocess (especially check_call and check_output).
Instance Attribute Summary collapse
-
#command ⇒ Array<String>
readonly
The command this process was invoked with.
-
#pid ⇒ Fixnum
readonly
The process ID of the spawned process.
-
#status ⇒ Object
readonly
Returns the value of attribute status.
-
#stderr ⇒ Object
readonly
Returns the value of attribute stderr.
-
#stdin ⇒ IO
readonly
The ‘IO` that is connected to this process’s ‘stdin`.
-
#stdout ⇒ IO
readonly
The ‘IO` that is connected to this process’s ‘stdout`.
Instance Method Summary collapse
-
#communicate(input = nil) ⇒ Array<String>
Write the (optional) input to the process’s ‘stdin`.
-
#drain_fd(fd, buf = nil) ⇒ true, false
Do nonblocking reads from ‘fd`, appending all data read into `buf`.
-
#initialize(cmd, opts = {}) {|process| ... } ⇒ Process
constructor
Create a new process.
-
#poll ⇒ ::Process::Status?
Poll the child, setting (and returning) its status.
-
#send_signal(signal) ⇒ Object
Does exactly what it says on the box.
-
#terminate ⇒ Object
Sends ‘SIGTERM` to the process.
-
#wait ⇒ ::Process::Status
Wait for the child to return, setting and returning the status of the child.
Constructor Details
#initialize(cmd, opts = {}) {|process| ... } ⇒ Process
Create a new process.
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# File 'lib/subprocess.rb', line 226 def initialize(cmd, opts={}, &blk) raise ArgumentError, "cmd must be an Array" unless Array === cmd raise ArgumentError, "cmd cannot be empty" if cmd.empty? @command = cmd # Figure out what file descriptors we should pass on to the child (and # make externally visible ourselves) @child_stdin, @stdin = parse_fd(opts[:stdin], 'r') @child_stdout, @stdout = parse_fd(opts[:stdout], 'w') unless opts[:stderr] == STDOUT @child_stderr, @stderr = parse_fd(opts[:stderr], 'w') end retained_fds = Set.new(opts[:retain_fds] || []) # A control pipe for ferrying errors back from the child control_r, control_w = IO.pipe @pid = fork do begin FileUtils.cd(opts[:cwd]) if opts[:cwd] ::STDIN.reopen(@child_stdin) if @child_stdin ::STDOUT.reopen(@child_stdout) if @child_stdout if opts[:stderr] == STDOUT ::STDERR.reopen(::STDOUT) else ::STDERR.reopen(@child_stderr) if @child_stderr end # Set up a new environment if we're requested to do so. if opts[:env] ENV.clear ENV.update(opts[:env]) end # Call the user back, maybe? opts[:preexec_fn].call if opts[:preexec_fn] = {close_others: true}.merge(opts.fetch(:exec_opts, {})) if opts[:retain_fds] retained_fds.each { |fd| [fd] = fd } end # Ruby's Kernel#exec will call an exec(3) variant if called with two # or more arguments, but when called with just a single argument will # spawn a subshell with that argument as the command. Since we always # want to call exec(3), we use the third exec form, which passes a # [cmdname, argv0] array as its first argument and never invokes a # subshell. exec([cmd[0], cmd[0]], *cmd[1..-1], ) rescue Exception => e # Dump all errors up to the parent through the control socket Marshal.dump(e, control_w) control_w.flush end # Something has gone terribly, terribly wrong if we're hitting this :( exit!(1) end # Meanwhile, in the parent process... # First, let's close some things we shouldn't have access to @child_stdin.close if our_fd?(opts[:stdin]) @child_stdout.close if our_fd?(opts[:stdout]) @child_stderr.close if our_fd?(opts[:stderr]) control_w.close # Any errors during the spawn process? We'll get past this point when the # child execs and the OS closes control_w begin e = Marshal.load(control_r) e = "Unknown Failure" unless e.is_a?(Exception) || e.is_a?(String) # Because we're throwing an exception and not returning a # Process, we need to make sure the child gets reaped wait raise e rescue EOFError # Nothing to read? Great! ensure control_r.close end # Everything is okay. Good job, team! blk.call(self) if blk end |
Instance Attribute Details
#command ⇒ Array<String> (readonly)
Returns The command this process was invoked with.
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# File 'lib/subprocess.rb', line 184 def command @command end |
#pid ⇒ Fixnum (readonly)
Returns The process ID of the spawned process.
184 |
# File 'lib/subprocess.rb', line 184 attr_reader :command, :pid, :status |
#status ⇒ Object (readonly)
Returns the value of attribute status.
184 |
# File 'lib/subprocess.rb', line 184 attr_reader :command, :pid, :status |
#stderr ⇒ Object (readonly)
Returns the value of attribute stderr.
175 |
# File 'lib/subprocess.rb', line 175 attr_reader :stdin, :stdout, :stderr |
#stdin ⇒ IO (readonly)
Returns The ‘IO` that is connected to this process’s ‘stdin`.
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# File 'lib/subprocess.rb', line 175 def stdin @stdin end |
#stdout ⇒ IO (readonly)
Returns The ‘IO` that is connected to this process’s ‘stdout`.
175 |
# File 'lib/subprocess.rb', line 175 attr_reader :stdin, :stdout, :stderr |
Instance Method Details
#communicate(input = nil) ⇒ Array<String>
Write the (optional) input to the process’s ‘stdin`. Also, read (and buffer in memory) the contents of `stdout` and `stderr`. Do this all using `IO::select`, so we don’t deadlock due to full pipe buffers.
This is only really useful if you set some of ‘:stdin`, `:stdout`, and `:stderr` to Subprocess::PIPE.
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# File 'lib/subprocess.rb', line 361 def communicate(input=nil) raise ArgumentError if !input.nil? && @stdin.nil? stdout, stderr = "", "" stdout_encoding = @stdout.external_encoding if @stdout stderr_encoding = @stderr.external_encoding if @stderr input = input.dup unless input.nil? @stdin.close if (input.nil? || input.empty?) && !@stdin.nil? self_read, self_write = IO.pipe self.class.catching_sigchld(pid, self_write) do wait_r = [@stdout, @stderr, self_read].compact wait_w = [input && @stdin].compact loop do ready_r, ready_w = select(wait_r, wait_w) # If the child exits, we still have to be sure to read any data left # in the pipes. So we poll the child, drain all the pipes, and *then* # check @status. # # It's very important that we do not call poll between draining the # pipes and checking @status. If we did, we open a race condition # where the child writes to stdout and exits in that brief window, # causing us to lose that data. poll if ready_r.include?(@stdout) if drain_fd(@stdout, stdout) wait_r.delete(@stdout) end end if ready_r.include?(@stderr) if drain_fd(@stderr, stderr) wait_r.delete(@stderr) end end if ready_r.include?(self_read) if drain_fd(self_read) raise "Unexpected internal error -- someone closed our self-pipe!" end end if ready_w.include?(@stdin) begin written = @stdin.write_nonblock(input) rescue EOFError # Maybe I shouldn't catch this... rescue Errno::EINTR end input[0...written] = '' if input.empty? @stdin.close wait_w.delete(@stdin) end end break if @status # If there's nothing left to wait for, we're done! break if wait_r.length == 0 && wait_w.length == 0 end end wait stdout.force_encoding(stdout_encoding) if stdout_encoding stderr.force_encoding(stderr_encoding) if stderr_encoding [stdout, stderr] end |
#drain_fd(fd, buf = nil) ⇒ true, false
Do nonblocking reads from ‘fd`, appending all data read into `buf`.
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# File 'lib/subprocess.rb', line 338 def drain_fd(fd, buf=nil) loop do tmp = fd.read_nonblock(4096) buf << tmp unless buf.nil? end rescue EOFError, Errno::EPIPE fd.close true rescue Errno::EINTR rescue Errno::EWOULDBLOCK, Errno::EAGAIN false end |
#poll ⇒ ::Process::Status?
Poll the child, setting (and returning) its status. If the child has not terminated, return nil and exit immediately
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# File 'lib/subprocess.rb', line 319 def poll @status ||= (::Process.waitpid2(@pid, ::Process::WNOHANG) || []).last end |
#send_signal(signal) ⇒ Object
Does exactly what it says on the box.
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# File 'lib/subprocess.rb', line 441 def send_signal(signal) ::Process.kill(signal, pid) end |
#terminate ⇒ Object
Sends ‘SIGTERM` to the process.
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# File 'lib/subprocess.rb', line 446 def terminate send_signal("TERM") end |
#wait ⇒ ::Process::Status
Wait for the child to return, setting and returning the status of the child.
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# File 'lib/subprocess.rb', line 327 def wait @status ||= ::Process.waitpid2(@pid).last end |