Shell Programming and Scripting

Hi,

I'm reading a csh setup script, and came across these lines:

Code:

################################

if (! $?PROJECT_ROOT) then
    setenv PROJECT_ROOT /proj/proj_123
endif

################################

Does the if endif command means, "if there is no variable named "PROJECT_ROOT", then set it to "/proj/proj_123" ?

What if there already exist a variable named "PROJECT_ROOT" ?

Moderator's Comments:

Please use code tags

nothing happens.

Is my assumption on the lines are correct? I'm new to scripting fyi :

"Does the if endif command means, "if there is no variable named "PROJECT_ROOT", then set it to "/proj/proj_123" ?"

if - is a logical branch and starts a distinct block of code

any
line in here
gets executed when the if statement is true

endif ends the block of code, it is a marker for the end of the if - block it does not affect logic.

Therefore if the variable is not defined, as the if statement asks, then any line of code up to but not including the endif gets executed.

The endif does nothing as rcdwayx explained.