Get name of process associated with PID

Question

The subject is the question -- I have the PID(s). Either I'm overlooking something or this is far more difficult than I expected (would be happy to hear differently). Do shell script routine would be fine.

Answer 1

Yesterday I assigned some credits to the responses to my post, without comment. For anyone actually interested, I do have some comments.
In terms of the way I initially presented my question, Camelot's response was most on target. I said I had a PID and wanted to get the related process name, and he pointed me at "lsof PID" (with a length enhancement). Typically, that gave a result like "Default" whereas the full name is actually "Default Folder X" -- a result of calling for the first word (only) in the COMMAND column of the lsof result.
Niel's responses covered some ground that I had explored and given up on.
But in fact I had actually gotten PID's from "lsof /", so all this seemed pretty circular; it seemed silly not to figure out how to get a complete process name from lsof / in the first place. To that end, Nils C. Anderson of the UNIX forum pointed me to "lsof -Fc /" as a way of getting the complete COMMAND column of lsof /. The result includes a couple alpha identifiers and some PID info that can be edited out, and what's worked best for me is: set COMlist to do shell script "lsof -Fc / | sed -e 's/^p.*//' -e 's/c//'" -- a fast one liner.
There remains one issue (see below), but this approach has provided the best process name list yet, at least for open files.
The remaining issue is this: a small but significant number of open files return the COMMAND in the form (file name)\xxxxxxxx. If I want to compare that to a list of actual file names, somehow I've got to get rid of the "\xxxxxxxxx" portion of the COMMAND, but (maybe I'm blind) the escape seems to defy attempts at doing that. E.g., do shell script "echo " & (COMMAND)&" | sed 's/\xxxxxxxxx//' returns an error, and I haven't found a way to add the second escape AS is looking for. If I should do a new post on this specific issue, tell me that.