Hi, so a program was prebuilt before my time here that names files (I assume) with the 'date +%j' because they all correspond to the current year, but in a 001-365 format. "Filename.212.gz" for example. I need to be able to grab one of these files and parse through it (done) but now they want it pretty with the actual date i.e. "July 28". Is there any quick way to use the linux 'date' cmd to my advantage? I would love to use something in place instead of taking up memory... I don't mind writing it out, but just thought I would ask. Thanks!

I've found a TON of programs on google about the gregorian calendar and conversions, but if there is an easier way - I'm all for it.

Here's your shell script. You set yday (day of year) and year (since 1900)

Ah nice!

I've always done this by passing epoch time of the # of days given, adjusted by timezone through localtime and grab the appropriate field in the resulting array.

This certainly saves some effort, thanks for the tip Mr C

You're welcome.

You can add a final parameter for specifying daylight saving time. isdst value of 0 or 1. I figured the OP wouldn't care about this since we're assuming midnight here.

There is a little known function in the date command to add an offset to a date string.

date -d "1 jan 2008 212 days"
Thu Jul 31 00:00:00 GMT+4 2008

Of course you can specify the exact date format for output:
date -d "1 jan 2008 212 days" +"%b %d"
Jul 31

Any offset can be added, but you have to tell what the number means, e.g. sec or days


jlinkels

Nice jlinkels.

Bonzer jlinkels!

You can also go backward:
Furthermore, you can combine different time units:

WOW! Very nice! Thank you!!!

Okay, I have another problem... This worked GREAT on my Suse and Ubuntu boxes, but I have a FREEBSD machine that the "date -d" is all screwed up... I found the man pages, but if anyone can help do the same thing as above, but with the freebsd version i would GREATLY appreciate it.

http://nixdoc.net/man-pages/FreeBSD/date.1.html

According to the man page, the -d option has a totally different meaning on FreeBSD. On Unix machines, where the -d option did not exist, I used a custom Fortran code which accepted a date in yyyymmdd format and a number of days to add or subtract. If you are experienced in programming you can try to write a C or a Fortran code to do the required operations. Or eventually you can write some function in python or in another scripting language that can manage dates.

Or eventually install the GNU date on FreeBSD, but sincerely I don't know if it is possible or if there is a precompiled package that provides such functionality.

Does the perl script I gave you now work?

You've run into the standard cross-platform utilities problem. This is an important requirement to mention at the beginning of your problem. Otherwise, as you found out, solutions won't work.

I generally try to keep portability in mind when I propose solutions.

Hmmm, never knew that BSD was so much different from Linux.

I have found python-parsedatetime which is a module able to parse a human expression date/time. Maybe it is easier than writing from scratch.

jlinkels

I would highly recommend this route. `date` is tried and true and will take things into account such as leap years, etc. You can install the GNU utilities on damn near everything including Solaris.