built-in gmtime() returning one month off?

snafu has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to write a program that stages files to later archive based off of either dates embedded in the filenames or if those don't exist then from the date of the mtime on the filesystem for each file.

Ok, so, that being said, I need the date to be as accurate as possible. However, after some tests I am finding that the mtime returned from stat() and then being converted to human readable format via Perl's built-in gmtime() that for some reason the month returned is one month off.

I find it more difficult to believe that there is something wrong with Perl versus something wrong with what I am doing. Please check my work and see if I am off somewhere.

First, I touch a file so I get the desired mtime that I am looking for. I check the mtime using a utility I wrote called macls. Here is the output...


MACtime for: "test_file_1_200008261030"
Mode(-rw-r--r-- => 0644) gvc(2000) gvcadm(104)  0 bytes  0 blocks
Modified time   ........ Sat Aug 26 09:30:00 2000
Access time     ........ Sat Aug 26 09:30:00 2000
Inode Change    ........ Tue Jun 18 12:14:19 2002

*******************************************************
MACtime for: "test_file_2_199504231930"
Mode(-rw-r--r-- => 0644) gvc(2000) gvcadm(104)  0 bytes  0 blocks
Modified time   ........ Sun Apr 23 18:30:00 1995
Access time     ........ Sun Apr 23 18:30:00 1995
Inode Change    ........ Tue Jun 18 12:14:39 2002

*******************************************************
MACtime for: "test_file_3_200506200200"
Mode(-rw-r--r-- => 0644) gvc(2000) gvcadm(104)  0 bytes  0 blocks
Modified time   ........ Mon Jun 20 01:00:00 2005
Access time     ........ Mon Jun 20 01:00:00 2005
Inode Change    ........ Tue Jun 18 12:15:00 2002

Total files checked : 4
Total size in bytes : 0
Total size in Kbytes: 0K
[download]

Note the strange and abnormal dates how they jump around and stuff =P jk. Anyway, so we know the dates are on the file system the way I want them. Oh, also note that the time stamp I used for the touch command is in the filename so I can reference it should the mtime get whacked in the moving of the files from place to place on the fs. One thing I just noticed is the actual time I specified for the touch command is off by one hour on the file system. Very interesting.

Ok. Now, I now do the following:

perl -e 'open(F,"test_file_1_200008261030");$date = (stat(F))[9];@date
+ = (eval((gmtime($date))[3,4,5]));print "@date\n"'

26 7 100
[download]

For everyone who doesn't know, the first number is the day, the second number is the month and the third number is the year - 1900. Everything is fine except the month value. Its off by a month.

What am I overlooking?

_ _ _ _ _ _ _ _ _ _
- Jim
Insert clever comment here...

Comment on built-in gmtime() returning one month off? Select or Download Code

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Re: built-in gmtime() returning one month off? by belg4mit (Prior) on Jun 18, 2002 at 19:03 UTC
gmtime, the range is 0-11 `-- perl -pew "s/\b;([mnst])/'$1/g"`	[reply]
Re: built-in gmtime() returning one month off? by insensate (Hermit) on Jun 18, 2002 at 19:07 UTC
The localtime and gmtime functions represent the month of the year as a digit between 0 and 11 (0 = January etc...). Add one to your month value to get the result you are looking for. `($day,$month,$year)=(gmtime)[3,4,5]; printf"02d-%02d-%04d",$month+1,$day,$year+1900;` [download] -Jason	[reply] [d/l]
Re: Re: built-in gmtime() returning one month off? by snafu (Chaplain) on Jun 18, 2002 at 19:10 UTC
Bah!! Somebody kick me please! :) Thanks to all. sigh _ _ _ _ _ _ _ _ _ _ - Jim Insert clever comment here...	[reply]
Re: Re: Re: built-in gmtime() returning one month off? by Juerd (Abbot) on Jun 18, 2002 at 21:31 UTC
Bah!! Somebody kick me please! :) Thanks to all. sigh /me kicks snafu :) Next time, RTFM first. On your local system, you can use `perldoc -f gmtime` to get the appropriate documentation. Don't code by trial-and-error. Always have a terminal open to access documentation :) - Yes, I reinvent wheels. - Spam: Visit eurotraQ.	[reply] [d/l]
Re: built-in gmtime() returning one month off? by grinder (Bishop) on Jun 18, 2002 at 19:32 UTC
So far the other responses have all given correct advice, however, you may still be wondering about the reason months are off by one. The reason the value is as it is is so that you may use it to index an array of month names, without wasting the first element. Thus, you could get the month name with something like: `my $month_name = (qw/Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec/)[$month];` [download] There is some method to the madness... print@_{sort keys %_},$/if%_=split//,'= & *a?b:e\f/h^h!j+n,o@o;r$s-t%t#u'	[reply] [d/l]
Re: built-in gmtime() returning one month off? by thelenm (Vicar) on Jun 18, 2002 at 19:08 UTC
It may just be that the month returned by gmtime is zero-based, so you'll need to add 1 to get the value you expect (e.g., 1 for January, etc.) -- Mike `-- just,my${.02}`	[reply]
Re: built-in gmtime() returning one month off? by Abigail-II (Bishop) on Jun 19, 2002 at 13:16 UTC
What am I overlooking? The documentation that comes with Perl? It would have been a lot easier to type `perldoc -f gmtime` than to write your message. Abigail	[reply]