> linux user wrote: > > > >>On Monday 23 May 2005 02:04, Deron Meranda wrote: > >> > >>>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 > >> > >>This is by far the most complete and understandable explanation > >>of environment > >>variables and exporting. Not just answers the question, but > also lets one > >>learn the concept behind it. I just wish that there be as many as > >>possible > >>such good answers on the list... :-)) > > > > > > Yes. It is very detailed. Here are a couple of minor details > to add to what's above. > > > > If a user exports an environment variable from a terminal it's > only good for that terminal. > > > > linux@example% export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:lib > > > > The above line sets the environment variable LD_LIBRARY_PATH to > the current LD_LIBRARY_PATH plus the relative lib directory. > > > > If you're using the bash shell, to view an entire list of > environment variables for a terminal just type "export". To make > permanent changes to environment variables, again if using the > bash shell, the user can go to their home location and edit the > .bashrc file. > > > > .bashrc example: > > > > LD_LIBRARY_PATH=$LD_LIBRARY_PATH:home/linux/lib > > > > After adding the above line to the .bashrc file, the load > library path will be the same for every terminal and doesn't have > to be set each time a new terminal is opened. > > > > If you want this path to be available to any terminal that is > open you will have to "source .bashrc" at the command prompt. > Otherwise, just close all active terminals and open new ones. > > > > > Errm don't you need to export that ie; > LD_LIBRARY_PATH=$LD_LIBRARY_PATH:home/linux/lib > export LD_LIBRARY_PATH No. Not in the .bashrc file. > > Regards. > > Rick
