Add tool "diff" for Linux and Unix (#3501)

* Update __init__.py

* Add files via upload

* Update diff.py

lisa/tools/__init__.py

@@ -27,6 +27,7 @@
 from .date import Date
 from .df import Df
 from .dhclient import Dhclient
+from .diff import Diff
 from .dmesg import Dmesg
 from .dnsmasq import Dnsmasq
 from .docker import Docker
@@ -140,6 +141,7 @@
     "Date",
     "Df",
     "Dhclient",
+    "Diff",
     "Dmesg",
     "Dnsmasq",
     "Docker",

lisa/tools/diff.py

@@ -0,0 +1,70 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+from pathlib import PurePath
+from typing import Optional
+
+from lisa.executable import Tool
+
+
+class Diff(Tool):
+    """
+    Diff is a tool class for comparing files or directories using the 'diff' command.
+
+    Attributes:
+        command (str): The command to be executed, which is 'diff'.
+        can_install (bool): Indicates whether the tool can be installed.
+            Always False for this tool.
+
+    Methods:
+        _check_exists() -> bool:
+            Checks if the tool exists. Always returns True for this tool.
+
+        comparefiles(
+            timeout: int = 600
+            Compares two files or directories.
+
+            Args:
+                src (PurePath): The source file or directory.
+                dest (PurePath): The destination file or directory.
+                cwd (Optional[PurePath]): The current working directory for the command.
+                Defaults to None.
+                sudo (bool): Whether to run the command with sudo. Defaults to False.
+                timeout (int): The timeout for the command in seconds. Defaults to 600.
+
+            Returns:
+                str: The output of the diff command.
+
+            Raises:
+                AssertionError: If the exit code of the diff command is not 0 or 1.
+    """
+
+    @property
+    def command(self) -> str:
+        return "diff"
+
+    @property
+    def can_install(self) -> bool:
+        return False
+
+    def comparefiles(
+        self,
+        src: PurePath,
+        dest: PurePath,
+        cwd: Optional[PurePath] = None,
+        sudo: bool = False,
+        timeout: int = 600,
+    ) -> str:
+        cmd = f"{self.node.get_str_path(src)} {self.node.get_str_path(dest)}"
+        result = self.run(
+            cmd,
+            force_run=True,
+            sudo=sudo,
+            cwd=cwd,
+            shell=True,
+            timeout=timeout,
+        )
+        # Diff generated difference between FILE1 FILE2 or DIR1 DIR2 or DIR FILE
+        # for FILE DIR
+        # EXit status is 0 if inputs are the same. 1 if different, 2 if trouble
+        result.assert_exit_code([0, 1], f"Diff Error: {result.stderr}")
+        return result.stdout