use tee to append to file instead of spawning copying and catenating files

Commander.py

@@ -1,21 +1,18 @@
+import os
 from robot.api.deco import library, keyword
 from robot.libraries.BuiltIn import BuiltIn
+from robot.libraries.Process import Process
 
 @library
 class Commander:
 
     @property
-    def OperatingSystem(self):
-        self._operatingsystem = self._operatingsystem or self.BuiltIn.get_library_instance('OperatingSystem')
-        return self._operatingsystem
-
-    @property
-    def Process(self):
+    def Process(self) -> Process:
         self._process = self._process or self.BuiltIn.get_library_instance('Process')
         return self._process
 
     @property
-    def BuiltIn(self):
+    def BuiltIn(self) -> BuiltIn:
         self._builtin = self._builtin or BuiltIn()
         return self._builtin
 
@@ -25,24 +22,32 @@ class Commander:
         self._operatingsystem = None
 
     @keyword
-    def execute_pipeline(self, *commands, stdout=None, append=False):
+    def execute_pipeline(self, *commands, cwd=None, stdout=None, append=False):
         procs = []
         append = (stdout and append) or False
-        if append:
-            self.OperatingSystem.append_to_file(stdout, '')
-            self.OperatingSystem.move_file(stdout, f'{stdout}.old')
-
-        procs.append(self.Process.start_process(*commands[0]))
-        prev = procs[-1]
+        procs.append(self.Process.start_process(
+            *commands[0], cwd=cwd,
+        ))
         for command in commands[1:-1]:
-            procs.append(self.Process.start_process(*command, stdin=prev.stdout))
-            prev = procs[-1]
+            procs.append(self.Process.start_process(
+                *command, cwd=cwd,
+                stdin=procs[-1].stdout,
+            ))
         procs.append(self.Process.start_process(
-            *commands[-1], stdin=prev.stdout, stdout=f'{stdout}.new' if append else stdout))
-        ret = self.Process.wait_for_process(procs[-1])
+            *commands[-1], cwd=cwd,
+            stdin=procs[-1].stdout,
+            stdout=None if append else stdout,
+        ))
         if append:
-            ret = self.Process.run_process('cat', f'{stdout}.old', f'{stdout}.new', stdout=stdout)
-            self.OperatingSystem.remove_file(f'{stdout}.new')
-            self.OperatingSystem.remove_file(f'{stdout}.old')
-        return ret
-
+            # set cwd like ProcessConfiguration does
+            cwd = os.path.normpath(cwd) if cwd else os.path.abspath('.')
+            # set output filename like ProcessConfiguration does
+            stdout = os.path.normpath(os.path.join(cwd, stdout))
+            procs.append(self.Process.start_process(
+                'tee', '-a', stdout,
+                cwd=cwd,
+                stdin=procs[-1].stdout,
+                stdout='DEVNULL',
+            ))
+        
+        return self.Process.wait_for_process(procs[-1])