> so, when a command is entered it winds its way "up" (or down) until a > match is found. hmm, think must I on this. Environment variables are private to each process. Although each process *usually* gets its initial set of variables by copying those from it's parent, from that point on they are different. A variable lookup does not go "up the chain" of processes...it only looks in the current process. You can see the current set of environment variables in a shell by using the "env" builtin command. For non-shell programs there is usually a language-dependent method to get to them. In C/C++ for instance there is the environ[] array as well as the getenv(3) library call. In Python you have the sys.environ dictionary. And so on for other languages. If you want to see the environment variables in some other process your choices are more restricted. Given that you have proper security permissions, you can look at the /proc/nnnn/environ file, where nnnn is the process ID number. The variables are separated by 0-valued bytes, so the easiest way to just peek at them is perhaps, cat /proc/12345/environ | xargs -0 -n 1 echo # that's a digit-zero in the "-0" They are usually listed unsorted, so you can also pipe it through the sort command. [The above technique is Linux-specific; other Unix-based OS's have slightly different mechanisms]. Now, as far as the export command...the shell (bash and others) is really just a simple interactive programming language. Like most programming languages it has it's own concept of a "variable". The shell's variables are actually distinct from environment variables, which the kernel itself keeps. The export command tells the shell that you want it to essentially equate the two....meaning that whenever you change the value of a shell variable, it will also implicitly change the value of a equivalently named environment variable. Environment variables will be inherited by any child processes the shell happens to start, shell variables will not be. Incidentally you only need to export a variable once; you don't need to keep exporting it every time you change it's value. -- Deron Meranda
