deamon help

[Blair P. Houghton]

In article <BZS.91Feb5105600 at world.std.com> bzs at world.std.com (Barry Shein) writes:
>Just write a shell script loop which uses awk to suck out the TIME
>field of the procs as reported by ps and see if it's changing or not.

Gack.  Scripts for daemons.  Barry, you should be ashamed. :-)

Write it in C and use popen(3).  (Use YACC for the parsing,
if you want it done to a crisp).  (Uh-oh.  My BSD is
showing.  Does SysV know popen?)

A stronger reason to use C is that ps(1) often runs fields
together; it can also munge columnar justification.  You'll
have to detect and work around those situations.  (If you
can characterize the various forms of run-together fields,
lex(1) can tokenize them together and then yacc(1) can parse
them apart).

For example (output of "ps alx | egrep 'TIME|foo'"):

      F UID   PID  PPID CP PRI NI ADDR  SZ  RSS WCHAN STAT TT  TIME COMMAND
94080012010 11236 11235255  96  41eba211194 9660       R N  pa143:58  (foo)
b0000013092 17289   244  7   1  017232  41   21 be598 S    10  0:00 egrep TIME|

PID 17829 is fine.  PID 11236 is a mess.  awk(1) and
perl(1) would barf up gnodes at this.  (Those of you who
smell challenge, smell aright.)

>For a problem like this I'll bet you a nickel crafting the whole thing
>in C using /dev/kmem etc will not be much faster than the above
>described script, and will take a week to get right instead of 30 minutes.

Better, use popen(3) and top(1).  Top usually gets the data
much faster than ps.  Why?  Who knows?  Could be anything
from superior skills among public-domain software developers
to abuse of /dev/null.

				--Blair
				  "My every keyword is copyright
				   someone else, these days..."