No. In fact it is a "variable". Suppose the following: i don't know where you installed a certain program, but i know how the place where the program is installed looks like because i work with it a lot. So, if you ask me where you can find the logs of the program, i'd tell you: "go to where you installed the program". In there, whereever that is, you find a directory "<somewhere>/logs" and inside of this you find a directory "<somewhere>/log/program-logs", ... Now, you might ask me something else about this program and again, i'd refer to the (to me unknown) location of the program as "<somewhere>" and direct you to some plcae relative to there.

This is what variables are for: you define them by assigning some value (in your case the value /usr/local/entity/project) to a name (data_dir) and then you can use it everywhere without needing to know the exact value of it. Just like i used the name "<somewhere>" above. I could have used a variable:

Code:

program_location= .....    <= you would have to fill in the actual path here, say: /usr/myprogram

and in this case the logs would have been there:

Code:

program_location=/usr/myprogram
cd $program_location/logs
cd $program_location/logs/program-logs

The second and third lines use the variable we have defined before: $program_location is first replaced by what we assigned to the name "program_location" before, only then "/logs" or respectively "/logs/program-logs" is appended. So the real commands read:

Code:

cd /usr/myprogram/logs
cd /usr/myprogram/program-logs

PATH is a special kind of variable. Or, rather, a normal variables (everything i said above applies) but with a special function. You see, a program is a certain file (where executable code is stored). To execute the program you have to write the full name of the program file:

Code:

/path/to/the/executable/file/of/my/program

As the pathes get longer this might be a lot of work to type. Computer people are in general of the lazy sort (this is why we use computers to do it for us). Since many programs are collected in a few directories (i.e. most of the systems commands are stored in /usr/bin) the PATH variable was invented. It holds a list of directories, separated by ":". The rule is: if a program is located in one of the directories in this list then you do not need to specify the path when calling it.

That means: your path looks like this:

Code:

PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/entity/bin

This is a list of directories: /usr/bin, /bin, /usr/sbin, /sbin and /usr/local/entity/bin. For instance there is a command cp (it copies files) located in /usr/bin. So, to call it and copy the file "file" to a new file called "new_file" you would have to use the command

Code:

/usr/bin/cp file new_file

But since /usr/bin is included in your PATH variable you can omit that and write:

Code:

cp file new_file

I hope this helps.

bakunin