Adding 'Vol." before the volume number in a plainnat bibliography

Question

I'm working out how to edit a .bst-file to customise a bibliography. I have made a number of changes, but I am struggling to work out how to add "Vol." to the reference before my volume. As you can see, I have edited the standard plainnat.bst below to as 'no.' before number and 'p.' before page, but this was just through trial and error and a good guess based on what was showing.

 FUNCTION {format.vol.num.pages}
{ volume field.or.null
  number empty$
     'skip$
    { "\penalty0 \ no. " number * "," * *
       volume empty$
        { "there's a number but no volume in " cite$ * warning$ }
        'skip$
      if$
    }
   if$
   pages empty$
    'skip$
    { duplicate$ empty$
        { pop$ format.pages }
       { "\penalty0 \ p. " * pages n.dashify * }
     if$
    }
  if$
}

Please can someone advice on what changes to make to add "vol." before my volume number.

Answer 1

The naive method

"Vol.~" volume field.or.null *

seems to work. This does no checking as to whether the volume field is empty or not.

If you want checking, try

volume empty$
  { "" }
  { "Vol.~" volume field.or.null * }
if$

Answer 2

I do not currently have a computer with LaTeX available, but as you are in a hurry, I'll give it a shot, hoping I remember the fairly arcane .bst-syntax well enough. I think this should do the trick for you:

FUNCTION {format.vol.num.pages}
{ volume field.or.null
  volume empty$
    'skip$
    { "Vol. " *  }
  if$number empty$
     'skip$
    { "\penalty0 \ no. " number * "," * *
       volume empty$
        { "there's a number but no volume in " cite$ * warning$ }
        'skip$
      if$
    }
   if$
pages empty$
 'skip$
 { duplicate$ empty$
     { pop$ format.pages }
    { "\penalty0 \ p. " * pages n.dashify * }
      if$
    }
  if$
}

Let me know how far you get with this. I can check back here on my phone or tablet, and I should be back at my computer in a few hours.