If you need to 'diff' two dmesg files, you will find that the timestamps cause diff-noise. Remove the timestamps so that you get to the underlying diff.

dmesg-diff

#!/bin/bash

# dmesg-diff
#  Kieran Bingham 2016
#  Public Domain
#
#  Strip out Linux Kernel timestamps when performing a diff on two dmesg files
#
#  Initial version as proof-of-concept, but already useful.
#  This could be extended to parse extra flags for diff for example
#  Uses bash temporary stream extensions to save creating tempory files

# Usage
#  dmesg-diff file1 file2

FILE1=$1
FILE2=$2

STRIP_TS='s/^\[[[:space:]+[:digit:].]*\]//'

# http://stackoverflow.com/questions/15841223/diff-while-ignoring-patterns-within-a-line-but-not-the-entire-line

diff -u \
	--label=$FILE1 <(sed $STRIP_TS $FILE1) \
	--label=$FILE2 <(sed $STRIP_TS $FILE2)