logfiles.py

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# Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
 
"""Utilitites for log file parsing and printing"""
 
import collections
import itertools
import re
import sys
 
def grep_with_context(f, pattern, lines = 100, print_head = True, print_tail = True):
    """Print errors in file `f` with the given number of context lines before/after
    the `pattern` (regex). In addition print head or tail of file if requested.
    """
    # See: https://stackoverflow.com/questions/36027227
 
    # Print first N lines:
    if print_head:
       sys.stdout.writelines(itertools.islice(f, lines))
 
    before = collections.deque(maxlen=lines)
    skipped = 0  # number of skipped lines
 
    def printBefore():
        '''Print the `before` buffer'''
        nonlocal skipped
        skipped -= len(before)
        if skipped > 0:
            sys.stdout.write('\n[Skipped %d line%s]\n\n' % (skipped, 's' if skipped>1 else ''))
        sys.stdout.writelines(before)
        before.clear()
        skipped = 0
 
    regex = re.compile(pattern)
    for line in f:
        if re.search(regex, line):
            printBefore()
            sys.stdout.write(line)
            sys.stdout.writelines(itertools.islice(f, lines))
        else:
            skipped += 1
            before.append(line)
 
    # Print the last N lines:
    if print_tail:
       printBefore()