shell_command: dev utility for executing linux commands

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

klippy/extras/shell_command.py

@@ -0,0 +1,98 @@
+# linux shell command execution utility
+#
+# Copyright (C) 2020  Eric Callahan <arksine.code@gmail.com>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import os
+import shlex
+import subprocess
+import logging
+
+class ShellCommand:
+    def __init__(self, printer, cmd):
+        self.printer = printer
+        self.name = cmd
+        self.gcode = self.printer.lookup_object('gcode')
+        self.output_cb = self.gcode.respond_info
+        cmd = os.path.expanduser(cmd)
+        self.command = shlex.split(cmd)
+        self.proc_fd = None
+        self.partial_output = ""
+
+    def _process_output(self, eventime):
+        if self.proc_fd is None:
+            return
+        try:
+            data = os.read(self.proc_fd, 4096)
+        except Exception:
+            pass
+        data = self.partial_output + data
+        if '\n' not in data:
+            self.partial_output = data
+            return
+        elif data[-1] != '\n':
+            split = data.rfind('\n') + 1
+            self.partial_output = data[split:]
+            data = data[:split]
+        try:
+            self.output_cb(data)
+        except Exception:
+            logging.exception("Error writing command output")
+
+    def set_output_callback(self, cb=None):
+        if cb is None:
+            self.output_cb = self.gcode.respond_info
+        else:
+            self.output_cb = cb
+
+    def run(self, timeout=2., verbose=True):
+        if not timeout:
+            # Fire and forget commands cannot be verbose as we can't
+            # clean up after the process terminates
+            verbose = False
+        reactor = self.printer.get_reactor()
+        try:
+            proc = subprocess.Popen(
+                self.command, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+        except Exception:
+            logging.exception(
+                "shell_command: Command {%s} failed" % (self.name))
+            raise self.gcode.error("Error running command {%s}" % (self.name))
+        if verbose:
+            self.proc_fd = proc.stdout.fileno()
+            self.gcode.respond_info("Running Command {%s}...:" % (self.name))
+            hdl = reactor.register_fd(self.proc_fd, self._process_output)
+        elif not timeout:
+            # fire and forget, return from execution
+            return
+        eventtime = reactor.monotonic()
+        endtime = eventtime + timeout
+        complete = False
+        while eventtime < endtime:
+            eventtime = reactor.pause(eventtime + .05)
+            if proc.poll() is not None:
+                complete = True
+                break
+        if not complete:
+            proc.terminate()
+        if verbose:
+            if self.partial_output:
+                self.output_cb(self.partial_output)
+                self.partial_output = ""
+            if complete:
+                msg = "Command {%s} finished\n" % (self.name)
+            else:
+                msg = "Command {%s} timed out" % (self.name)
+            self.gcode.respond_info(msg)
+            reactor.unregister_fd(hdl)
+            self.proc_fd = None
+
+class PrinterShellCommand:
+    def __init__(self, config):
+        self.printer = config.get_printer()
+
+    def load_shell_command(self, cmd):
+        return ShellCommand(self.printer, cmd)
+
+def load_config(config):
+    return PrinterShellCommand(config)