topic Re: Need help ASAP in Operating System - Linux

Need help ASAP

OFC_EDM — Thu, 09 Mar 2006 12:11:21 GMT

ok this really isn't the most critical of issues except I need to get this figured out ASAP to make my boss happy.

I need to store in a varable the date for
2 hours ago

Now this seemed simple. Except I started thinking about certain conditions:
1) What if it's 1 am? The date two hours ago is from the previous day. I can't just take the hour and subract 2.
2) leap year
3) what if it's 1 am on jan 1st; same as issue 1) but the year is also affected.

anyone have a solution to this?

I'm trying to accomplish this is regular shell (posix) scripting utilizing utilities like sed /awk and any built-in posix functions.

But if perl or something else is the answer then I'll just have to go that route.

Any and all help appreciated.

Cheers,
Kevin

Re: Need help ASAP

Steven E. Protter — Thu, 09 Mar 2006 12:18:28 GMT

Shalom Kevin

http://hpux.ws/merijn/caljd-2.23.sh

http://hpux.ws/merijn/caljd-2.2.pl

Both handle date calculations that you describe with reasonable efficiency.

Maintained by our fearless point leader, A. Clay Stephenson.

SEP

Re: Need help ASAP

A. Clay Stephenson — Thu, 09 Mar 2006 12:28:40 GMT

TM=$(perl -e 'print scalar localtime(time - 7200)')
echo "Two hours ago was ${TM}"

You can also extract individual fields from Perl's localtime function, if you like.

Re: Need help ASAP

OFC_EDM — Thu, 09 Mar 2006 12:45:48 GMT

Interesting Mr Stephenson.

Your command works but I get the following errors: (script posted below)
./2hoursago.sh
Two hours ago was Thu Mar 9 08:43:45 2006
./2hoursago.sh[7]: /: Execute permission denied.
./2hoursago.sh[8]: /: Execute permission denied.
./2hoursago.sh[9]: /: Execute permission denied.
./2hoursago.sh[10]: /: Execute permission denied.
./2hoursago.sh[11]: /: Execute permission denied.

Here's my script:

#!/usr/bin/sh
TM=$(perl -e 'print scalar localtime(time - 7200)')
echo "Two hours ago was ${TM}"

any ideas?

Re: Need help ASAP

OFC_EDM — Thu, 09 Mar 2006 12:49:09 GMT

Fixed it and it now works.
There were some odd characters which found their way into my script.

THANK YOU

Re: Need help ASAP

OFC_EDM — Thu, 09 Mar 2006 12:51:22 GMT

Thank you both for your replies.

I realized I must now learn perl. For that was way too easy.

Thank you Mr. Protter for the other links as well. They will be very useful.

Re: Need help ASAP

OFC_EDM — Thu, 09 Mar 2006 13:01:42 GMT

Just as a thank you for the help and to save someone some time here's the simple code to see the different times:

#!/usr/bin/sh

TM2h=$(perl -e 'print scalar localtime(time - 7200)') # 7200 seconds = 2 hours
TM8h=$(perl -e 'print scalar localtime(time - 28800)') # 28800 seconds = 8 hours
TM24h=$(perl -e 'print scalar localtime(time - 86400)') # 86400 seconds = 24 hours
TM1w=$(perl -e 'print scalar localtime(time - 604800)') # 604800 seconds = 1 week

echo " 2 hours ago was ${TM2h}"
echo " 8 hours ago was ${TM8h}"
echo "24 hours ago was ${TM24h}"
echo " 1 week ago was ${TM1w}"

Re: Need help ASAP

Senthil Kumar .A_1 — Thu, 09 Mar 2006 13:05:37 GMT

Hi Kevin,

Thanks for the query, this has given me some opportunity me do some c programming/sys programming. Last done during my college days in the year 2000.

Just write a c program..

---------------------------------

#include ;
#include ;
int main () {
time_t t,a;
t=time(&t);
a=t-172800;
printf("%s\n",ctime(&a));
}

---------------------------------

Just compile it and execute the ./a.out

,voila it will always print the the day which is 2 days before.

172800 is 42 hours in seconds.

Regards,
Senthil Kumar .A

Re: Need help ASAP

Senthil Kumar .A_1 — Thu, 09 Mar 2006 13:08:55 GMT

Sorry 2 hours is it,i thought 2 days..

then subract just.. 7200

--------------------------------

#include ;
#include ;
int main () {
time_t t,a;
t=time(&t);
a=t-7200;
printf("%s\n",ctime(&a));
}

------------------------------

Here u do not require to worry about ..leap years,time zone, months etc..

Regards,
Senthil Kumar .A

Re: Need help ASAP

Senthil Kumar .A_1 — Thu, 09 Mar 2006 13:17:58 GMT

Hi guys,

This has given me a reason to learn perl. Hats off to Clay stevenson. WOW that perl command was too cool . I did not see others post when I was working with my c program. Sorry.

By the way ,As far as UNIX is concerned, perl has beaten C... WOW unbelievable.

Regards,
Senthil Kumar .A