'tail -f' alternative which colors any given tag/word: usage: ctail path/to/file regex_to_color_1 regex_to_color_2 ... regex_to_color_N

ctail.py

#!/usr/bin/env python
# encoding: utf-8
'''
ctail -- colored tail

ctail is a simple 'tail -f' alternative which colors given regular expressions matches


@author:     Otger Ballester
            
@license:    Apache License 2.0\nhttp://www.apache.org/licenses/LICENSE-2.0

@contact:    otger@libtronics.com
@deffield    updated: Updated
'''

import sys
import os
import time
import re
from optparse import OptionParser

__all__ = []
__version__ = 0.1
__date__ = '2013-09-25'
__updated__ = '2013-10-03'

DEBUG = 0
TESTRUN = 0
PROFILE = 0

class CLIError(Exception):
    '''Generic exception to raise and log different fatal errors.'''
#     def __init__(self, msg):
#         super(CLIError).__init__(type(self))
#         self.msg = "E: %s" % msg
    def __str__(self):
        return self.message
    def __unicode__(self):
        return self.message
    def __repr__(self, *args, **kwargs):
        return self.message

colours = {}
# Regular
colours["Black"]="\033[0;30m"
colours["Red"]="\033[0;31m"
colours["Green"]="\033[0;32m"
colours["Yellow"]="\033[0;33m"
colours["Blue"]="\033[0;34m"
colours["Purple"]="\033[0;35m"
colours["Cyan"]="\033[0;36m"
colours["White"]="\033[0;37m"
#Bold
colours["BBlack"]="\033[1;30m"
colours["BRed"]="\033[1;31m"
colours["BGreen"]="\033[1;32m"
colours["BYellow"]="\033[1;33m"
colours["BBlue"]="\033[1;34m"
colours["BPurple"]="\033[1;35m"
colours["BCyan"]="\033[1;36m"
colours["BWhite"]="\033[1;37m"
# High Intensity
colours["IBlack"]="\033[0;90m"
colours["IRed"]="\033[0;91m"
colours["IGreen"]="\033[0;92m"
colours["IYellow"]="\033[0;93m"
colours["IBlue"]="\033[0;94m"
colours["IPurple"]="\033[0;95m"
colours["ICyan"]="\033[0;96m"
colours["IWhite"]="\033[0;97m"
# Bold High Intensity
colours["BIBlack"]="\033[1;90m"
colours["BIRed"]="\033[1;91m"
colours["BIGreen"]="\033[1;92m"
colours["BIYellow"]="\033[1;93m"
colours["BIBlue"]="\033[1;94m"
colours["BIPurple"]="\033[1;95m"
colours["BICyan"]="\033[1;96m"
colours["BIWhite"]="\033[1;97m"

colour_close = "\033[0m"

colour_list = ['BRed', 'BGreen', 'BYellow', 'BBlue', 'BPurple', 'BCyan', 'IRed', 'IGreen', 'IYellow', 'IBlue', 'IPurple', 'ICyan']

def regexes_coloring(what, regexes, regexes_colors):
    for regex in regexes:
        what = re.sub(regex, '{c}\g<0>{cc}'.format(c=regexes_colors[regex], cc=colour_close), what)
    return what

def seek_last_n_lines_position(fp, nlines=10):
    '''
    Return fp positioned at start of last nlines
    Inspired in code found at:  http://stackoverflow.com/questions/136168/get-last-n-lines-of-a-file-with-python-similar-to-tail
    '''
    BLOCKSIZE = 1023
    fp.seek(0, 2)
    pending_lines = nlines
    fp_pos = fp.tell()
    block = -1
    
    while 1:
        if fp_pos > BLOCKSIZE:
            fp.seek(block*BLOCKSIZE, 2)
            data = fp.read(BLOCKSIZE)
        else:
            ## file too small to contain nlines lines, return positioned at start 
            fp.seek(0,0)
            data = fp.read(fp_pos)
            block=0

        lines_in_block = data.count('\n')
        if pending_lines <= lines_in_block:
            end = -1
            for _ in range(pending_lines):
                end = data.rfind('\n', 0, end)
            if block==0:
                fp.seek(end +len('\n'),0)
            else:
                fp.seek(block*BLOCKSIZE + end +len('\n'),2)
            return fp
        elif block == 0:
            fp.seek(0,0)
            return fp
        
        pending_lines -= lines_in_block
        fp_pos -= BLOCKSIZE
        block -= 1
    

def main(argv=None):
    '''Command line options.'''
    datetime_regex = r'\d{4}[-.]?\d{2}[-.]?\d{2} \d{2}:\d{2}:\d{2}(?:,\d{3})?'
    program_name = os.path.basename(sys.argv[0])
    program_version = "v0.1"
    program_build_date = "%s" % __updated__
 
    program_version_string = '%%prog %s (%s)' % (program_version, program_build_date)
    #program_usage = '''usage: spam two eggs''' # optional - will be autogenerated by optparse
    program_longdesc = '''''' # optional - give further explanation about what the program does
    program_license = "Copyright 2013 Otger Ballester (otger)                                            \
                Licensed under the Apache License 2.0\nhttp://www.apache.org/licenses/LICENSE-2.0"
 
    if argv is None:
        argv = sys.argv[1:]
    try:
        # setup option parser
        parser = OptionParser(version=program_version_string, epilog=program_longdesc, description=program_license)
        parser.add_option("-d", action="store_true", dest="color_date", help="color date times in format: yyyy-mm-dd HH:MM:SS")
        parser.add_option("-l", default=10, dest="nlines", type="int", help="show last lines from file [default: %default]")
        # process options
        (opts, args) = parser.parse_args(argv)
        
        if len(args) < 1:
            raise CLIError('Path to file must be provided')
        
        file_path = args[0]
        if not os.path.exists(file_path):
            raise CLIError('File ({0}) does not exist'.format(file_path))
        if len(args) > 1: 
            regexes = args[1:]
        else: regexes = []
        
        if opts.color_date: regexes.insert(0, datetime_regex)
        
        color_mod = len(colour_list)
        ## requires python 2.7+
        ## color_regexes = {regex: colours[colour_list[ix%color_mod]] for ix, regex in enumerate(regexes)}
        color_regexes = dict((regex, colours[colour_list[ix%color_mod]]) for ix, regex in enumerate(regexes))
        
        
        # MAIN BODY #
        fp = open(file_path, 'r')
        #fp.seek(0, 2)
        fp = seek_last_n_lines_position(fp, opts.nlines)
        if regexes:
            while True:
                new = fp.readline()
                # Once all lines are read this just returns ''
                # until the file changes and a new line appears
                if new:
                    sys.stdout.write(regexes_coloring(new, regexes, color_regexes))
                else:
                    time.sleep(0.05)
        else:
            while True:
                new = fp.readline()
                # Once all lines are read this just returns ''
                # until the file changes and a new line appears
                if new:
                    sys.stdout.write(new)
                else:
                    time.sleep(0.05)
            
    except KeyboardInterrupt:
        ##Clean exit when pressing Ctrl + c
        sys.stdout.write('\n')
        return 0
    except Exception, e:
        import traceback
        indent = len(program_name) * " "
        sys.stderr.write(program_name + ": " + repr(e) + "\n")
        sys.stderr.write(indent + "  for help use --help\n")
        if DEBUG:
            print "\nTraceback:"
            traceback.print_exc()
        return 2


if __name__ == "__main__":
    sys.exit(main())