Shell Programming and Scripting

Does anyone know how to calculate a calendar date since Jan 1, 2000 (this is day 1). I am using CSH with a Solaris system (no GNU products installed).

Example:
Input from the user (number of days):
4444

Output (dd mmm yy)
02 mar 12

---------- Post updated at 09:40 PM ---------- Previous update was at 09:35 PM ----------

actually I need to the output to have the whole year so 2012 instead of 12.

You are better off using Perl instead of csh. Perl is available in Solaris

Code:

$ cat a.pl
#! /usr/bin/perl

@M=('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');
($x,$x,$x,$mday,$mon,$yr)=localtime(946656000+86400*$ARGV[0]);
printf("%02d %s %4d",$mday,$M[$mon],$yr+1900);


$ ./a.pl 4444
02 Mar 2012

Thanks so much...I'll give it a try tomorrow. I am not familar with perl...could you explain the code.

If you are on Solaris 10, the ksh93 (Korn) shell is available to you.

In this shell, date arithmetic is fully supported

Code:

$ printf "%(%D)T\n" "Jan 1 2000 + 4444 days"
03/02/12
$

Thanks for the info I didn't realize. How do you call this Korn shell? Is it #! /usr/bin/korn
Also, how do you get the date in dd mmm yyyy format? For example 26 Mar 2012?

This list provides index to the abbr month name. The 4th column returns from the 'localtime' will give the index of the month. Eg. 2 means Mar. List index starts from 0

Code:

@M=('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');

localtime is a Perl built-in function that returns second, minute, hour, ..... In our case, we only need the day of the month ($mday), month ($mon), and year ($yr). 946656000 is the epoch time for 2000-01-01, we just need to add the additional seconds for the input days

Code:

($x,$x,$x,$mday,$mon,$yr)=localtime(946656000+86400*$ARGV[0]);

$yr returns 100 for year 2000, therefore we need to add 1900. Also, we need the month in abbr form and therefore we need to refer to the value based on the position in the list @M

Code:

printf("%02d %s %4d",$mday,$M[$mon],$yr+1900);

My preference is #!/usr/bin/env ksh which will invoke it provided the binary is in a directory specified in your PATH. I use this method because I believe it is more portable and on most of my systems I build the latest version of Kshell and install it outside of the system default (/usr/bin/ksh or /usr/local/bin/ksh); I want to ensure that I'm invoking my build rather than the version that was included in the distribution.