jobs -Z example?

jobs -Z example?

[Atom Smasher]

can someone point me to an example of "jobs -Z" in action?

thanks...


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Re: jobs -Z example?

[Bart Schaefer]

On Mar 16,  7:24am, Atom Smasher wrote:
}
} can someone point me to an example of "jobs -Z" in action?

torch% ps $$
  PID TTY      STAT   TIME COMMAND
 5249 pts/4    Ss     0:00 Src/zsh -f
torch% jobs -Z "You can't see me"
torch% ps $$                     
  PID TTY      STAT   TIME COMMAND
 5249 pts/4    Ss     0:00 You can't see me
torch% print $(< /proc/$$/cmdline )
You can't see me
torch% 

If you mean an explanation of why you'd *want* to do that sort of
thing, the reasons can be a bit obscure.  As one real-world example,
at work we run a job queuing system where a controller process passes
tasks to a set of worker processes.  The worker processes are each a
subshell of a "foreman" script which runs in an infinite loop to keep
track of how many workers are active and to start a new one when one
exits.

So the script at startup runs something like
    jobs -Z "worker:foreman"
and when each subshell starts it runs
    jobs -Z "worker:task"

That way, we can differentiate in "ps" output which process is which,
rather than having them all appear to be copies of the same script.
If we want to shut the system down cleanly, we kill the foreman and
let the workers die off as their tasks complete.

Yes, we could do this by having the foreman write it's PID to a file
instead, etc.  This just makes it obvious when running "top" or other
system monitoring.

Re: jobs -Z example?

[Atom Smasher]

On Sun, 15 Mar 2009, Bart Schaefer wrote:

> } can someone point me to an example of "jobs -Z" in action?
>
> torch% ps $$
>  PID TTY      STAT   TIME COMMAND
> 5249 pts/4    Ss     0:00 Src/zsh -f
> torch% jobs -Z "You can't see me"
> torch% ps $$
>  PID TTY      STAT   TIME COMMAND
> 5249 pts/4    Ss     0:00 You can't see me
> torch% print $(< /proc/$$/cmdline )
> You can't see me
> torch%
=====================

that's pretty much what i expected, but it's not working on freeBSD.

7.1-STABLE + zsh 4.3.9 (amd64-portbld-freebsd7.1)
6.2-RELEASE + zsh 4.3.6 (amd64-portbld-freebsd6.2)

maybe it's a freeBSD/amd64 thing? it seems to work fine on linux (P3).


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Re: jobs -Z example?

[Christian Schneider]

Thus spake Atom Smasher (atom@smasher.org):
> On Sun, 15 Mar 2009, Bart Schaefer wrote:
>> } can someone point me to an example of "jobs -Z" in action?
>>
>> torch% ps $$
>>  PID TTY      STAT   TIME COMMAND
>> 5249 pts/4    Ss     0:00 Src/zsh -f
>> torch% jobs -Z "You can't see me"
>> torch% ps $$
>>  PID TTY      STAT   TIME COMMAND
>> 5249 pts/4    Ss     0:00 You can't see me
>> torch% print $(< /proc/$$/cmdline )
>> You can't see me
>> torch%
> =====================
>
> that's pretty much what i expected, but it's not working on freeBSD.
>
> 7.1-STABLE + zsh 4.3.9 (amd64-portbld-freebsd7.1)
> 6.2-RELEASE + zsh 4.3.6 (amd64-portbld-freebsd6.2)
>
> maybe it's a freeBSD/amd64 thing? it seems to work fine on linux (P3).

Works fine on Linux 2.6.26 and OpenBSD 4.4 (both i386)
#v+
(dope@dreckskind) : (~): zsh --version
zsh 4.3.6 (i386-unknown-openbsd4.4)
(dope@dreckskind) : (~): jobs -Z "You can't see me"
(dope@dreckskind) : (~): ps $$
  PID TT  STAT       TIME COMMAND
  29389 p0  Ss      0:00.32 You can't see me (zsh)
(dope@dreckskind) : (~):
#v-

Re: jobs -Z example?

[Bart Schaefer]

On Mar 16,  9:49am, Atom Smasher wrote:
}
} that's pretty much what i expected, but it's not working on freeBSD.

Some OSs stash the original command and environment so that you can't
conceal them this way, because malware sometimes attempts to disguise
itself with this trick so it's considered more secure to disallow it.

Try this:

    perl -e '$0 = "Test hiding command"; sleep 10;' & ps $!

If perl is able to do it but zsh is not, then it's just that FreeBSD
has a different mechanism for it and we may be able to patch zsh.

Re: jobs -Z example?

[Atom Smasher]

On Sun, 15 Mar 2009, Bart Schaefer wrote:

> Some OSs stash the original command and environment so that you can't 
> conceal them this way, because malware sometimes attempts to disguise 
> itself with this trick so it's considered more secure to disallow it.
>
> Try this:
>
>    perl -e '$0 = "Test hiding command"; sleep 10;' & ps $!
>
> If perl is able to do it but zsh is not, then it's just that FreeBSD has 
> a different mechanism for it and we may be able to patch zsh.
=====================

weird.... (FreeBSD 6.2-RELEASE amd64) it sometimes works under bash, 
doesn't work under zsh. see below. similar results in a 7.1-STABLE jail, 
but it seems more likely to work as desired.


* bash:
for n in {1..10}; do
    perl -e '$0 = "Test hiding command"; sleep 10;' &
done ; ps -t p7
[1] 5247
[2] 5248
[3] 5249
[4] 5250
[5] 5251
[6] 5252
[7] 5253
[8] 5254
[9] 5255
[10] 5256
   PID  TT  STAT      TIME COMMAND
   945  p7  Is     0:00.87 zsh
  4843  p7  S      0:00.15 bash
  5247  p7  S      0:00.01 Test hiding command (perl5.8.8)
  5248  p7  S      0:00.01 Test hiding command (perl5.8.8)
  5249  p7  S      0:00.01 Test hiding command (perl5.8.8)
  5250  p7  S      0:00.01 Test hiding command (perl5.8.8)
  5251  p7  R      0:00.00 perl -e $0 = "Test hiding command"; sleep 10; (perl5.8.8)
  5252  p7  S      0:00.01 Test hiding command (perl5.8.8)
  5253  p7  RL     0:00.00 perl -e $0 = "Test hiding command"; sleep 10; (perl5.8.8)
  5254  p7  R      0:00.00 perl -e $0 = "Test hiding command"; sleep 10; (perl5.8.8)
  5255  p7  S      0:00.01 Test hiding command (perl5.8.8)
  5256  p7  D      0:00.00 perl -e $0 = "Test hiding command"; sleep 10; (perl5.8.8)
  5257  p7  R+     0:00.00 ps -t p7

* zsh:
for n in {1..10}; do
    perl -e '$0 = "Test hiding command"; sleep 10;' &
done ; ps -t p7
[2] 5341
[3] 5342
[4] 5343
[5] 5344
[6] 5345
[7] 5346
[8] 5347
[9] 5348
[10] 5349
[11] 5350
   PID  TT  STAT      TIME COMMAND
   945  p7  Ss     0:01.00 zsh
  5341  p7  RN     0:00.00 zsh
  5342  p7  RNL    0:00.00 zsh
  5343  p7  DN     0:00.00 zsh
  5344  p7  DN     0:00.00 zsh
  5345  p7  DN     0:00.00 zsh
  5346  p7  DN     0:00.00 zsh
  5347  p7  DN     0:00.00 zsh
  5348  p7  DN     0:00.00 zsh
  5349  p7  DN     0:00.00 zsh
  5350  p7  DN     0:00.00 zsh
  5351  p7  R+     0:00.00 ps -t p7




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Re: jobs -Z example?

[Bart Schaefer]

On Mar 16, 10:41am, Atom Smasher wrote:
}
} On Sun, 15 Mar 2009, Bart Schaefer wrote:
} 
} > Try this:
} >
} >    perl -e '$0 = "Test hiding command"; sleep 10;' & ps $!
} >
} > If perl is able to do it but zsh is not, then it's just that FreeBSD has 
} > a different mechanism for it and we may be able to patch zsh.
} =====================
} 
} weird.... (FreeBSD 6.2-RELEASE amd64) it sometimes works under bash, 
} doesn't work under zsh. see below. similar results in a 7.1-STABLE jail, 
} but it seems more likely to work as desired.

Oh, there's probably a race condition then.  Try this instead:

  perl -e '$0 = "Test hiding command"; sleep 10;' & sleep 2; ps $!

The extra sleep in the parent shell will give perl a bit longer to get
going.

Your evidence so far indicates that assigning to $0 in perl is able
to change the command, so there must be something perl is doing that
"jobs -Z" is not doing.

Re: jobs -Z example?

[Atom Smasher]

On Sun, 15 Mar 2009, Bart Schaefer wrote:

> Oh, there's probably a race condition then.  Try this instead:
>
>  perl -e '$0 = "Test hiding command"; sleep 10;' & sleep 2; ps $!
>
> The extra sleep in the parent shell will give perl a bit longer to get 
> going.
=================

that works.


> Your evidence so far indicates that assigning to $0 in perl is able to 
> change the command, so there must be something perl is doing that "jobs 
> -Z" is not doing.
===================

seems like it.

thanks...


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 	 Ningauble shrugged. "You're a hero. You should know."
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Re: jobs -Z example?

[Dan Nelson]

In the last episode (Mar 16), Atom Smasher said:
> On Sun, 15 Mar 2009, Bart Schaefer wrote:
> 
> > Oh, there's probably a race condition then.  Try this instead:
> >
> >  perl -e '$0 = "Test hiding command"; sleep 10;' & sleep 2; ps $!
> >
> > The extra sleep in the parent shell will give perl a bit longer to get 
> > going.
> =================
> 
> that works.

In case it stops working later, all of the *BSDs provide a setproctitle()
function to cleanly reset what shows up in ps output.  Rewriting argv[0] may
cause problems, especially if you started out with a small commandline and
environment, or if you have called setenv/putenv/unsetenv.

-- 
	Dan Nelson
	dnelson@allantgroup.com

Re: jobs -Z example?

[Bart Schaefer]

On Mar 15,  9:07pm, Dan Nelson wrote:
}
} In case it stops working later, all of the *BSDs provide a setproctitle()

I see there's been some discussion about adding setproctitle() to glibc.

Let's try this.


diff -ru -x CVS zsh-forge/current/configure.ac zsh-4.0/configure.ac
--- zsh-forge/current/configure.ac	2009-03-08 14:01:12.000000000 -0700
+++ zsh-4.0/configure.ac	2009-03-15 20:59:52.000000000 -0700
@@ -1885,6 +1885,11 @@
   AC_DEFINE(USE_GETCWD)
 fi
 
+dnl CHECK FOR setproctitle() FOR jobs -Z / ARGV0
+AH_TEMPLATE([HAVE_SETPROCTITLE],
+[Define to 1 if the system supports this call to change process name])
+AC_SEARCH_LIBS(setproctitle, util, AC_DEFINE(HAVE_SETPROCTITLE))
+
 dnl -------------
 dnl CHECK FOR NIS
 dnl -------------
diff -ru -x CVS zsh-forge/current/Src/jobs.c zsh-4.0/Src/jobs.c
--- zsh-forge/current/Src/jobs.c	2009-03-14 23:22:20.000000000 -0700
+++ zsh-4.0/Src/jobs.c	2009-03-15 21:03:13.000000000 -0700
@@ -1572,12 +1572,14 @@
     return returnval;
 }
 
+#ifndef HAVE_SETPROCTITLE
 /* For jobs -Z (which modifies the shell's name as seen in ps listings).  *
  * hackzero is the start of the safely writable space, and hackspace is   *
  * its length, excluding a final NUL terminator that will always be left. */
 
 static char *hackzero;
 static int hackspace;
+#endif
 
 
 /* Initialise job handling. */
@@ -1600,6 +1602,7 @@
     jobtabsize = MAXJOBS_ALLOC;
     memset(jobtab, 0, init_bytes);
 
+#ifndef HAVE_SETPROCTITLE
     /*
      * Initialise the jobs -Z system.  The technique is borrowed from
      * perl: check through the argument and environment space, to see
@@ -1622,6 +1625,7 @@
     }
     done:
     hackspace = p - hackzero;
+#endif
 }
 
 
@@ -1718,10 +1722,14 @@
 	}
 	queue_signals();
 	unmetafy(*argv, &len);
+#ifdef HAVE_SETPROCTITLE
+	setproctitle("%s", *argv);
+#else
 	if(len > hackspace)
 	    len = hackspace;
 	memcpy(hackzero, *argv, len);
 	memset(hackzero + len, 0, hackspace - len);
+#endif
 	unqueue_signals();
 	return 0;
     }

Re: jobs -Z example?

[Bart Schaefer]

On Mar 15,  9:08pm, Bart Schaefer wrote:
}
} +AC_SEARCH_LIBS(setproctitle, util, AC_DEFINE(HAVE_SETPROCTITLE))

Actually the following is a bit more complete for configure.ac.

(Ignore the "4.0" in the directory name, it's the same CVS sandbox I've
been using for years and have never bothered to rename.)

--- zsh-forge/current/configure.ac	2009-03-08 14:01:12.000000000 -0700
+++ zsh-4.0/configure.ac	2009-03-15 21:26:28.000000000 -0700
@@ -1885,6 +1885,12 @@
   AC_DEFINE(USE_GETCWD)
 fi
 
+dnl CHECK FOR setproctitle() FOR jobs -Z / ARGV0
+AH_TEMPLATE([HAVE_SETPROCTITLE],
+[Define to 1 if the system supports `setproctitle' to change process name])
+AC_CHECK_FUNC(setproctitle,AC_DEFINE(HAVE_SETPROCTITLE),
+AC_SEARCH_LIBS(setproctitle,util,AC_DEFINE(HAVE_SETPROCTITLE)))
+
 dnl -------------
 dnl CHECK FOR NIS
 dnl -------------