Run linux command in ruby

Question

I'm trying to do the following..

   if "ps | grep -e file" then
      true;
   else
      false;

What would I need to do to make the string n the if statement execute the linux command listed?

Answer 1

Simply use system("command"). It'll return true if the command was successfully executed.

EDIT Just read your question again, and I believe that what you're looking for is this:

if `ps | grep -e file`.empty? # no matches
  true
else
  false
end

Answer 2

Don't have to call grep. Just call ps and let Ruby find the things you want.

if `ps`["file"]
  ...
else
  ...
end

Answer 3

Linux ps has a -C switch to check for a specific program name:

if "ps -C file" then
   true;
else
   false;

however - if you have a construct like

if (predicate) then true; else false; 

it should be the same as

(predicate) 

Answer 4

You can run your Linux Command like this

`echo "done"`

This will print done as output.