MANNS%DBNPIB5.BITNET@cunyvm.cuny.edu (Jochen Manns, PI der Uni Bonn, 732738/3611) (11/03/90)
Dear UNIX-Experts,
perhaps some of you can give me an answer of two UNIX questions:
- is it possible for a process to become a processes parent? In
Detail: I've got a job manager starting processes and controlling
them especially when they die to gather statistics and so on.
Now if the job manager dies and restarts again there no problem
to save its internal state i.e. all the processes it started and
recover this information from a disk file but all the children
have got some other parents (indeed, the new parent is always
process 1). So how can I attach to those processes again. And:
why aren't they killed when the job manager is killed (in fact
we like the way the did NOT die, but I would like to understand
this)?
- is there a way to access (argc,argv) from anywhere in a program?
In Detail: somewhere deeply nested in a library a subroutine
descided that it will need the commandline arguments of the
process but there is no way to get it through the usage of
parameters. For me it would be enough to get the whole line
instead of (argc,argv).
We are running UNIX V.3 on a DG AViiON 300.
Thank you in advance
Jochen Manns
Physikalisches Institut der Universitaet Bonn
Nussallee 12
5300 Bonn 1
(West Germany)gwyn@smoke.brl.mil (Doug Gwyn) (11/03/90)
In article <24928@adm.BRL.MIL> MANNS%DBNPIB5.BITNET@cunyvm.cuny.edu (Jochen Manns, PI der Uni Bonn, 732738/3611) writes: > - is it possible for a process to become a processes parent? I assume you mean, when the process did not start out as the other process's parent. The answer is, it is not supposed to happen, except for process # 1, the "init" process, which inherits as children all processes whose original parents terminate before they do. >So how can I attach to those processes again. You cannot, at least not through any means I could recommend. >... why aren't they killed when the job manager is killed ...? Why should they be? UNIX allows signals to be sent to individual processes or to entire "process groups". Unless something is specifically attempting to signal a process group, it will affect only one process. If the signal is self- generated, as for abnormal termination, only the process that generates the signal receives it. > - is there a way to access (argc,argv) from anywhere in a program? The only portable method is for the main() function to store them in some global variables. Some versions of UNIX do have "secret" global variables that are set up like that by the run-time start-up module, but you cannot rely on it across all environments.
brnstnd@kramden.acf.nyu.edu (Dan Bernstein) (11/04/90)
In article <14326@smoke.brl.mil> gwyn@smoke.brl.mil (Doug Gwyn) writes: > In article <24928@adm.BRL.MIL> MANNS%DBNPIB5.BITNET@cunyvm.cuny.edu (Jochen Manns, PI der Uni Bonn, 732738/3611) writes: > >So how can I attach to those processes again. > You cannot, at least not through any means I could recommend. But if he were using a BSD system, he could reattach through my pty program. As in the following: % sess foo (then this shell dies for some reason) % sess reconnect xx (where xx is the name of the session to reattach to) BSD wins. As usual. ---Dan
boyd@necisa.ho.necisa.oz (Boyd Roberts) (11/05/90)
In article <24928@adm.BRL.MIL> MANNS%DBNPIB5.BITNET@cunyvm.cuny.edu (Jochen Manns, PI der Uni Bonn, 732738/3611) writes: > > - is it possible for a process to become a processes parent? In No, the parent/child child relationship can only be created via fork(2). You can't re-parent an arbitary process. Of course, init (process 1) is a special case. Processes whose parent exits before them have their parent process id change to be that of init when the parent exits. > - is there a way to access (argc,argv) from anywhere in a program? Yes, declare: int gargc; char *gargv[]; as globals and in main() go: main(argc, argv) int argc; char *argv[]; { gargc = argc; gargv = argv; ... } Isn't this one a FAQ in comp.lang.c? Boyd Roberts boyd@necisa.ho.necisa.oz.au ``When the going gets wierd, the weird turn pro...''