Initial ftail implementation

.gitmodules

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+[submodule "console_bottombar"]
+	path = console_bottombar
+	url = https://git.mount-mockery.de/pylib/console_bottombar.git
+[submodule "task"]
+	path = task
+	url = https://git.mount-mockery.de/pylib/task.git

console_bottombar

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+Subproject commit c9d7f78f6d0feeeb5e14e4ca6a8ca22ce1c81165

ftail.py

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+import argparse
+from console_bottombar import BottomBar
+import os
+import re
+import sys
+import tail
+import task
+
+VERSION = "0.1.0"
+
+HELPTEXT = """
+F1: Get this help message
+F2: Set a filter (regular expression) for the topic of a message
+    Examples:
+    * "/gfw/.*/main_light/" to get everything with "/gfw/" before "/main_light/"
+    * "^zigbee.*(?>!logging)$" to get everything starting with "zigbee" and not ending with "logging"
+    * "^(?!shellies).*/dirk/.*temperature$" to get everything not starting with "shellies" followed by "/dirk/" and ends with "temperature"
+F12: Quit ftail
+
+'c': Clear screen
+'q': Quit
+"""
+
+
+def tail_parser(line):
+    global my_bb
+
+    try:
+        match = len(re.findall(my_bb.get_entry('msg_re'), line)) > 0
+    except re.error:
+        print('No valid regular expression (%s). No filter active.' % my_bb.get_entry('msg_re'))
+        match = True
+
+    if match:
+        sys.stdout.write(line)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description='This is a mqtt sniffer.')
+    parser.add_argument('logfile')  # , nargs='+' for >= 1
+
+    args = parser.parse_args()
+
+
+    if not os.access(args.logfile, os.R_OK):
+        print("Error: File %s is not readable!" % logfile)
+        sys.exit(1)
+    else:
+
+        #
+        # Background tail task
+        #
+        tp = tail.Tail(args.logfile)
+        tp.register_callback(tail_parser)
+        my_tail = task.delayed(0.1, tp.follow, 0.1)
+
+        #
+        # Bottombar
+        #
+        my_bb = BottomBar(VERSION, label='ftail')
+        my_bb.add_entry('help', 1, my_bb.FUNC_INFO, '[F1] Help', infotext=HELPTEXT)
+        my_bb.add_entry('msg_re', 2, my_bb.FUNC_TEXT, label='[F2] Filter', default="")
+        my_bb.add_entry('quit', 12, my_bb.FUNC_QUIT, "Quit", label='[F12]', right=True)
+
+        my_tail.run()
+        my_bb.run()
+
+        my_tail.stop()

tail.py

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+#!/usr/bin/env python
+
+'''
+Python-Tail - Unix tail follow implementation in Python. 
+
+python-tail can be used to monitor changes to a file.
+
+Example:
+    import tail
+
+    # Create a tail instance
+    t = tail.Tail('file-to-be-followed')
+
+    # Register a callback function to be called when a new line is found in the followed file. 
+    # If no callback function is registered, new lines would be printed to standard out.
+    t.register_callback(callback_function)
+
+    # Follow the file with 5 seconds as sleep time between iterations. 
+    # If sleep time is not provided 1 second is used as the default time.
+    t.follow(s=5) '''
+
+# Author - Kasun Herath <kasunh01 at gmail.com>
+# Source - https://github.com/kasun/python-tail
+
+import os
+import sys
+import time
+
+class Tail(object):
+    ''' Represents a tail command. '''
+    def __init__(self, tailed_file):
+        ''' Initiate a Tail instance.
+            Check for file validity, assigns callback function to standard out.
+            
+            Arguments:
+                tailed_file - File to be followed. '''
+
+        self.check_file_validity(tailed_file)
+        self.tailed_file = tailed_file
+        self.callback = sys.stdout.write
+
+    def follow(self, s=1):
+        ''' Do a tail follow. If a callback function is registered it is called with every new line. 
+        Else printed to standard out.
+    
+        Arguments:
+            s - Number of seconds to wait between each iteration; Defaults to 1. '''
+
+        with open(self.tailed_file) as file_:
+            # Go to the end of file
+            file_.seek(0,2)
+            while True:
+                curr_position = file_.tell()
+                line = file_.readline()
+                if not line:
+                    file_.seek(curr_position)
+                    time.sleep(s)
+                else:
+                    self.callback(line)
+
+    def register_callback(self, func):
+        ''' Overrides default callback function to provided function. '''
+        self.callback = func
+
+    def check_file_validity(self, file_):
+        ''' Check whether the a given file exists, readable and is a file '''
+        if not os.access(file_, os.F_OK):
+            raise TailError("File '%s' does not exist" % (file_))
+        if not os.access(file_, os.R_OK):
+            raise TailError("File '%s' not readable" % (file_))
+        if os.path.isdir(file_):
+            raise TailError("File '%s' is a directory" % (file_))
+
+class TailError(Exception):
+    def __init__(self, msg):
+        self.message = msg
+    def __str__(self):
+        return self.message

task

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+Subproject commit af35e83d1f07fd4cb9070bdb77cf1f3bdda3a463