thank you for answering but you don't answer correctly to my question. Maybe I don't ask it correctly...
I have found since I posted the first message this partial solution :
[[NSFileManager defaultManager] currentDirectoryPath]
This returns the path as a NSString to acceed to the current application. This could be a solution for my problem.
So you understand that I'm programming in Cocoa(Objective-C). As I know/understand it, I can't acceed from my class to the argv variable. So the previous way I typed (using a NSFileManager) is a right solution. But if I'm trying to do it, is to execute a program with a NSPipe. This program is part of my project, so I will put them together. With this solution I must put it in the same folder than my application, but I would like to make it easier for the user, putting it into the application folder, so something like "/Applications/MyProgramFodler/MyProgram.app/theProgramToPipe". But you understand that someone can change the name of the program. So it is not a complete solution.
For now I only can put it into : "/Applications/MyProgramFodler/plugins/theProgramToPipe"
So can anybody help me ?
thank you,
Pierre.