read last reboot-cause from symlink file

show/main.py

@@ -1806,14 +1806,30 @@ def mmu():
 @click.argument('history', required=False, type=click.Choice(["history"]))
 def reboot_cause(history):
     """Show cause of reboot"""
-    if history:
-        REBOOT_CAUSE_TABLE = "REBOOT_CAUSE"
-        TABLE_NAME_SEPARATOR = '|'
+    REBOOT_CAUSE_DIR = "/host/reboot-cause/"
+    PREVIOUS_REBOOT_CAUSE_DIR = "/host/reboot-cause/previous-reboot-cause/"
+    PREVIOUS_REBOOT_CAUSE_FILE = REBOOT_CAUSE_DIR + "previous-reboot-cause.txt"
+    USER_ISSUE_REBOOT_CAUSE_REGEX ="User issued \'{}\' command [User: {}, Time: {}]"
+    REBOOT_CAUSE_UNKNOWN = "Unknown"
+
+    def read_last_reboot_cause():
+        last_reboot_cause = REBOOT_CAUSE_UNKNOWN
+        # Read the last previous reboot cause
+        if os.path.exists(PREVIOUS_REBOOT_CAUSE_FILE):
+            with open(PREVIOUS_REBOOT_CAUSE_FILE, "r") as last_cause_file:
+                data = json.load(last_cause_file)
+                if data['user']:
+                    last_reboot_cause = USER_ISSUE_REBOOT_CAUSE_REGEX.format(data['cause'], data['user'], data['time'])
+                else:
+                    last_reboot_cause = "{}".format(data['cause'])
+        return last_reboot_cause
 
+    def read_reboot_cause_dbs():
+        REBOOT_CAUSE_TABLE_NAME = "REBOOT_CAUSE"
+        TABLE_NAME_SEPARATOR = '|'
         db = SonicV2Connector(host='127.0.0.1')
         db.connect(db.STATE_DB, False)   # Make one attempt only
-
-        prefix = REBOOT_CAUSE_TABLE + TABLE_NAME_SEPARATOR
+        prefix = REBOOT_CAUSE_TABLE_NAME + TABLE_NAME_SEPARATOR
         _hash = '{}{}'.format(prefix, '*')
         table_keys = db.keys(db.STATE_DB, _hash)
         table_keys.sort(reverse=True)
@@ -1847,26 +1863,16 @@ def remove_prefix(text, prefix):
                 r.append("")
             else:
                 r.append(entry['comment'])
-
             table.append(r)
+        return table
 
+    if not history:
+        click.echo(read_last_reboot_cause())
+    else:
+        table = read_reboot_cause_dbs()
         header = ['name', 'cause', 'time', 'user', 'comment']
         click.echo(tabulate(table, header))
 
-    else:
-        PREVIOUS_REBOOT_CAUSE_FILE = "/host/reboot-cause/previous-reboot-cause.txt"
-
-        # At boot time, PREVIOUS_REBOOT_CAUSE_FILE is generated based on
-        # the contents of the 'reboot cause' file as it was left when the device
-        # went down for reboot. This file should always be created at boot,
-        # but check first just in case it's not present.
-        if not os.path.isfile(PREVIOUS_REBOOT_CAUSE_FILE):
-            click.echo("Unable to determine cause of previous reboot\n")
-        else:
-            cmd = "cat {}".format(PREVIOUS_REBOOT_CAUSE_FILE)
-            proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, shell=True)
-            click.echo(proc.stdout.read())
-
 
 #
 # 'line' command ("show line")

tests/show_reboot_cause.py

@@ -0,0 +1,84 @@
+import os
+import sys
+import textwrap
+
+import mock
+from click.testing import CliRunner
+
+test_path = os.path.dirname(os.path.abspath(__file__))
+modules_path = os.path.dirname(test_path)
+sys.path.insert(0, modules_path)
+
+import show.main as show
+
+
+TEST_REBOOT_CAUSE = "warm-reboot"
+TEST_USER = "admin"
+TEST_REBOOT_TIME = "Fri Oct  9 04:51:47 UTC 2020"
+
+
+"""
+    Note: The following 'show reboot-cause' commands simply call other SONiC
+    CLI utilities, so the unit tests for the other utilities are expected
+    to cover testing their functionality:
+
+        show reboot-cause
+        show reboot-cause history
+"""
+
+class TestShowRebootCause(object):
+    @classmethod
+    def setup_class(cls):
+        print("SETUP")
+        os.environ["UTILITIES_UNIT_TESTING"] = "1"
+
+    def generate_hist_table(self):
+        table = []
+        for i in 2:
+            r = []
+            if i == 1:
+                r.append("2020_10_09_04_53_58")
+                r.append("warm-reboot")
+                r.append("Fri Oct  9 04:51:47 UTC 2020")
+                r.append("admin")
+                r.append("")
+            else:
+                r.append("2020_10_09_02_33_06")
+                r.append("reboot")
+                r.append("2020_10_09_02_33_06")
+                r.append("admin")
+                r.append("")
+            table.append(r)
+        return table
+
+    # Test 'show reboot-cause'
+    def test_reboot_cause(self):
+        expected_output = """\
+            User issued \'{}\' command [User: {}, Time: {}]
+            """.format(TEST_REBOOT_CAUSE, TEST_USER, TEST_REBOOT_TIME)
+
+        with mock.patch("show.main.read_last_reboot_cause",
+                        return_value={"User issued \'warm-reboot\' command [User: admin, Time: Fri Oct  9 04:51:47 UTC 2020]"}):
+            runner = CliRunner()
+            result = runner.invoke(show.cli.commands["reboot-cause"], [])
+            assert result.output == textwrap.dedent(expected_output)
+
+    # Test 'show reboot-cause history'
+    def test_reboot_cause_history(self):
+        expected_output = """\
+name                 cause        time                          user    comment
+-------------------  -----------  ----------------------------  ------  ---------
+2020_10_09_04_53_58  warm-reboot  Fri Oct  9 04:51:47 UTC 2020  admin
+2020_10_09_02_33_06  reboot       Fri Oct  9 02:29:44 UTC 2020  admin
+"""
+        with mock.patch("show.main.read_reboot_cause_dbs",
+                        return_value={generate_hist_table()}
+            runner = CliRunner()
+            result = runner.invoke(show.cli.commands["reboot-cause"].commands[history], [])
+            assert result.output == expected_output
+
+    @classmethod
+    def teardown_class(cls):
+        print("TEARDOWN")
+        os.environ["PATH"] = os.pathsep.join(os.environ["PATH"].split(os.pathsep)[:-1])
+        os.environ["UTILITIES_UNIT_TESTING"] = "0"