Program name from PID?

[Guy Harris]

>Given a process id, how can I find out the name of the process it belongs
>to?

Others have noted various ways of fetching various information about a
process that could be considered the "name" of the process.  The two
bits of information that could be considered the process's "name" are:

	1) the "u_comm" field from the process's U area.  This is the
	   first N characters of the last component of the pathname of
	   the last program "exec"ed by the process (or the last "#!"
	   script - many systems arrange that it be the name of the
	   script, rather than the name of the interpreter on the "#!"
	   line).

	2) something extracted from the "command line" for the process. 
	   On some systems, this may appear in the U area as a character
	   string; on other systems, it may have to be extracted from
	   the top of the process's stack.

	   In the former case, the first token in that string will be
	   whatever was passed as "argv[0]" when the last "exec" was
	   done; by convention, this is usually either the full pathname
	   of the last program (or #! script) "exec"ed by the process),
	   but it need not be - see my followup to the message here with
	   the subject line "Unknown process on sparc".

	   In the latter case, the above applies; in addition, the
	   process can overwrite that string with whatever it wants to,
	   and some programs, in fact, do so.

In other words, make sure you know what you want to do with that "name",
and make sure that the "name" you're fetching provides the information
you need....