What is a dot profile and what does it do? over all where can i find it. i need to make some changes in the same and hence need the .profile

thx a lot guyz.

Tell us what do you need to do so we can help better.

"A profile" can be lots of things. But since you wrote ".profile" (with a dot in front of it) I assume that you mean the bash initialization file. If that's the case, you can create such file in your home directory if it doesn't exist. If you want it to run globally for all users you could use /etc/profile instead (you will have to be root to be able to edit that one).

Read the "INVOCATION" section of the bash man page to read about these and the rest of the rc files for bash.

Hie.

I was installing QT version 3. and then it says if you have a Bash shell you gotto write some stuff in .profile

Thanks a lot.

should i use the bash_profile to write it or do i create a new .profile?? and in which directory ??

If you tell us what exactly do you want to do, it'll be easier to help you. There are 2 configuration files in your home directory that might be of interest for you:
.bash_profile
.bashrc
You can assign all your aliases there
Here you can find out the difference between the two files.

For system-wide configuration there's /etc/profile

As I told you in my other post, in your home directory. I would use either .bash_profile or .bashrc instead, or both of them, to be sure. These files will take precedence over any other. Note that ~/.profile won't be read if ~/.bash_profile or ~/.bash_login exist. As I also said in my other post, this info is in the "INVOCATION" section of the bash man page.