Hello
I have a perl script that runs a software build on NT4. The final stage
of this build creates a binary file called "gsm_gp_flash.abs". I want to
compare this to the previous instance of this file to see if anything
has changed. These *.abs files contain a date stamp, so even running a
diff utility on the 2 files will report a difference.
If I run NT's "fc" command on 2 of the files that were built using
exactly the same source fles (so in effect are the same apart from the
date stamp of when they were built) the difference looks like this (note
there is a blank line at the end of the output as well)
Comparing files ..\OBJ\gsm_gp_flash.abs and ..\OBJ\GSM_GP_FLASH_PREV.ABS
***** ..\OBJ\gsm_gp_flash.abs
%6.6s %9.9s
Sep 11 2002
20:26:10
Disconnecting...
***** ..\OBJ\GSM_GP_FLASH_PREV.ABS
%6.6s %9.9s
Sep 10 2002
20:25:34
Disconnecting...
*****
<---end of output
If that's all that gets output (allowing for different dates/times) then
I know there's no need to retest the *.abs file.
Now the trouble I'm having is that I can' get what I thought would be a
relativly strightforward pattern matching exercise to work. The snippet
of the perl script that collects the diff output and does the test is
my $prev_abs="..\\obj\\gsm_gp_flash_prev.abs";
my $abs_file="..\\obj\\gsm_gp_flash.abs";
my $months='(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)';
# collect the output of NT fc (file compare) command
$diff_abs = `fc /W $abs_file $prev_abs 2>&1`;
if($diff_abs =~
/
^Comparing files $abs_file and $prev_abs$
^\*\*\*\*\* $abs_file$
^%6\.6s %9\.9s$
^$months \d{1,2} \d\d\d\d$
^\d\d:\d\d:\d\d$
^Disconnecting\.\.\.$
^\*\*\*\*\* $prev_abs$
^%6.6s %9.9s$
^$months \d{1,2} \d\d\d\d$
^\d\d:\d\d:\d\d$
^Disconnecting\.\.\.$
^\*\*\*\*\*$
^$
/omi
)
{
print "file only differ by embedded date\n";
}
I thought that using the /m modifier ought to allow me to delineate each
logical line of the string with ^.....$
To check I haven't made a basic goof with each line of the regular
expression that matches each line of the output above I've taken each
line of the output and tested them indivdually against each line of the
regular expression like so:
$_ = "Comparing files ..\OBJ\gsm_gp_flash.abs and
...\OBJ\GSM_GP_FLASH_PREV.ABS";
print "OK\n" if /^Comparing files $abs_file and $prev_abs$ /;
...etc for each line of output, and it worked.
I've also tried using the /s modifier and putting a "." at the end of
each line to match newlines, but again I can't get it to match.
I suppose I could take the approach of just checking the length of the
$diff_abs string, it will always be a constant size for files that only
differ by their embedded dates, but I like to know what I'm missing with
the regular expression method. If anyone can see an obvious mistake or
put me straight on my understanding of multiline matching modifiers I'd
be grateful!
Best wishes
Reg Smith
PS - if anyone was wondering why I'm calling NT's fc files compare
utility rather than say cygwin diff or even comparing the files in perl,
it's because cygwin diff doesn't report the actual diffs (just if they
are different, it's a binary file) and the files are quite big to think
about opening for reading (57 meg). Also fc with it's /W (ignore
whitespace diffs) is actually very fast, virtually instantaneous with my
two test files
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