I've taken a project to work upon tracing of runtime activities on unix system into a log file. Like, to implement a program which will show the log of everything happened in past, including many requirements, like applications i used (with the time of access), kind of files/directories i opened, closed, created, deleted(with the time), etc.

Please suggest me something to do it in a better way.

You can get the source code for the shell(s) used, find the command line parsing section and stick a logging function in there (had to do this once to roll-my-own security logs). This would record every program or utility users executed, but only from the command line, so no record of what they did in, say, a text editor. If I remember correctly, some of the shell programs support logging (I think Korn Shell does, BASH may -- could be wrong about both of those though).

You can also get the secure version of the operating system and turn on the logging (which logs every blasted thing everybody does). Get hold of the vendor to find out about that -- be warned that the secure version are meant for high-security servers and the logs will be mammoth if you turn on everything.

Use Google looking for "secure unix" or possibly "secure linux" and see what turns up.

Hope this helps some.

For interactive users you may want to look at http://sourceforge.net/projects/rootsh/.
This may be a bit over the top, but have a read of the first page (Linux) http://www.linux.com/learn/tutorials...-linux-servers
If you're looking at Solaris, a lot of the tools mentioned there also apply, but as of Sol 10 we also have DTrace, a very fine tool.

In general though, as mentioned by Tronayne, if you start logging everything, watch out for disk space...