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gzip -lNv does not output internal timestamp's year

From: Scott-Fleming, Ian
Subject: gzip -lNv does not output internal timestamp's year
Date: Mon, 11 Feb 2013 07:33:39 +0000

Observed on RedHat 6 & Mac OS X 10.6.8
gzip versions:

RedHat 6:  gzip 1.3.12
Mac OS X 10.6.8:  gzip 1.4

Problem:  gzip -lNv only shows the month, day and time of time stamp, but does 
not show the year.
Thus code which is attempting to get original file's timestamp using "gzip 
-lNv" cannot determine the full internal timestamp.

Year is obviously stored, because the correct original timestamp is applied 
when unzipping with gunzip -N.
(Workaround is shown below)

tst$ ls -l testgz.txt
-rw-r--r--. 1 iscottfl geosciences 111542 Nov 30  2005 testgz.txt
tst$ stat -c %y testgz.txt
2005-11-30 04:15:28.000000000 -0600
address@hidden:/data/gcm_cmip5/tst$ gzip -N testgz.txt
address@hidden:/data/gcm_cmip5/tst$ ls -l testgz.txt.gz
-rw-r--r--. 1 iscottfl geosciences 5789 Nov 30  2005 testgz.txt.gz
tst$ stat -c %y testgz.txt.gz
2005-11-30 04:15:28.000000000 -0600
tst$ gzip -lNv testgz.txt.gz
method  crc     date  time           compressed        uncompressed  ratio 
defla 66f170b1 Nov 30 04:15                5789              111542  94.8% 

tst$ touch testgz.txt.gz
tst$ ls -l testgz.txt.gz
-rw-r--r--. 1 iscottfl geosciences 5789 Feb 11 01:15 testgz.txt.gz

# workaround:
tst$ file  testgz.txt.gz
testgz.txt.gz: gzip compressed data, was "testgz.txt", from Unix, last 
modified: Wed Nov 30 04:15:28 2005
# extract internal timestamp for later use
tst$ tstamp=$(date "+%s" -d "$(file -b testgz.txt.gz | awk '{print $10 " " $11 
" " $12 " " $13 " " $14}')")
tst$ echo $tstamp

As shown in last few lines, workaround is to parse the timestamp from the 
"file" utility output instead of gzip, so my world has not fallen to pieces as 
a result of gzip not reporting the year.  However, I noticed the problem while 
developing a script to verify downloaded & zipped files (and spent a grumbling 
hour or so finding the workaround.)

I imagine you are aware of this, and consider it a feature rather than a bug, 
and have good reason for what is in the code, but felt it worth an email to 
point it out, just in case.

Thanks for your attention, and the courtesy of a reply if you have time and 


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