Help Understanding Terminal's Command OS X 10.11.5 on a Mid 2011 iMac. I'm new to development on OS X and am trying to understand enough to figure out a Ruby path issue I'm having. I ran Inspector on Terminal and was surprised by the complexity of the command.



Instead of something like /bin/bash it is

login -pfl mark /bin/bash -c 'exec -la bash /bin/bash'

I don't understand how all these parts work together, or how the result differs from /bin/bash.
the login command is used to login to the unix system of OSX.
to learn more about it type 


  man login


As an example if you have a terminal window open and you are also logged into the GUI desktop you are logged in 2 times.
you can see how many sessions you have open by typing uptime
example:

7:52  up 23:49, 2 users, load averages: 1.43 1.53 1.50


the 2 users are your terminal window and your OS X gui.

if you open another terminal window and run uptime again you will see 3 users.

17:53  up 23:50, 3 users, load averages: 1.47 1.51 1.50


The command shown in the inspector is the command used for the terminal to login to UNIX.  Not what command is running in the terminal session. 
You can see what programs the terminal is running in the process info section of the inspector. You are only running login and bash in the screen shot you have uploaded.

To see the command of a running process select it in the inspector click the gear and click copy command. Paste it somewhere else.