eric@ux.acs.umn.edu (Merlinus Ambrosius) (11/10/90)
Can you explain why in this piece of code, fork() is returning a value
other than -1 or 0? When it works fine in other situations in the same
program? I tried changing
switch (fork ()) {
to
switch (fix = fork ()) {
where fix is declared as an int, no difference (as expected), fix does get
the pid of the child.
switch (fork ()) {
case -1:
Msg (errno, "fork");
/*NOTREACHED*/
case 0:
break;
default:
Attacher ();
/*NOTREACHED*/
}
It always ends up in the default case, which shouldn't be happening.
For now, I'm just going to stick a break in the default before it calls
Attacher(), but any ideas on what could be going on here would be wonderful.
Thanks,
Eric
--
/----------"Oh carrots are divine, you get a dozen for dime, its maaaagic."--
|Eric (the "Mentat-Philosopher") Hendrickson University of Minnesota
|eric@ux.acs.umn.edu ehend@hp370b.cfsmo.honeywell.com The game is afoot!
\---"What does 'masochist' and 'amnesia' mean? Beats me, I don't know."----gwyn@smoke.brl.mil (Doug Gwyn) (11/10/90)
In article <2691@ux.acs.umn.edu> eric@ux.acs.umn.edu (Merlinus Ambrosius) writes: >Can you explain why in this piece of code, fork() is returning a value >other than -1 or 0? Because fork() returns: -1 if unable to create another process 0 in the newly created process branch the process id of the new process, in the parent branch By the way, this is a UNIX-specific question, not a C language question. >... any ideas on what could be going on here would be wonderful. I would think they would be necessary.
ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) (11/10/90)
In article <2691@ux.acs.umn.edu>, eric@ux.acs.umn.edu (Merlinus Ambrosius) writes: > Can you explain why in this piece of code, fork() is returning a value > other than -1 or 0? Because it ought to. RTFM. If you're talking about the UNIX fork(2) system call, it yields one of three results: -1 => something went wrong, we've still just one process and this is it 0 => forking worked, and _this_ process is the child N => forking worked, _this_ process is the parent, and the child process has process it N. If you are going to wait for the child to finish, you _need_ this number. (Look at the DIAGNOSTICS section of the fork(2) manual page.) > |Eric (the "Mentat-Philosopher") Hendrickson University of Minnesota Um, if you're a Mentat, how come you need a computer? Mentats were supposed to be the human replacements for computers after the Butlerian Jihad. -- The problem about real life is that moving one's knight to QB3 may always be replied to with a lob across the net. --Alasdair Macintyre.
dak@sq.sq.com (David A Keldsen) (11/15/90)
>In article <2691@ux.acs.umn.edu>, (Merlinus Ambrosius) writes: [A question about fork()] ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes: >Because it ought to. RTFM. [...deleted to remove useful content...] >> |Eric (the "Mentat-Philosopher") Hendrickson University of Minnesota >Um, if you're a Mentat, how come you need a computer? Mentats were >supposed to be the human replacements for computers after the Butlerian Jihad. Well, obviously this mentat is working on a hidden project on Ix. Recall that Ix skirted the limits of what was legal... It would be called "Plan Ix," I suppose. Which just goes to show, this *really should* be in comp.unix.questions. ;-) Dak -- David A. 'Dak' Keldsen of SoftQuad, Inc. email: dak@sq.com phone: 416-963-8337 "You needn't go on making remarks like that," Humpty Dumpty said: "they're not sensible, and they put me out." -- _Through the Looking Glass & What Alice Found There_ by Lewis Carroll
eager@ringworld.Eng.Sun.COM (Michael J. Eager) (11/15/90)
In article <2691@ux.acs.umn.edu> eric@ux.acs.umn.edu (Merlinus Ambrosius) writes: >Can you explain why in this piece of code, fork() is returning a value >other than -1 or 0? When it works fine in other situations in the same > > switch (fork ()) { > case -1: > Msg (errno, "fork"); > /*NOTREACHED*/ > case 0: > break; > default: > Attacher (); > /*NOTREACHED*/ > } RTFM :-) RETURN VALUES On success, fork() returns 0 to the child process and returns the process ID of the child process to the parent process. On failure, fork() returns -1 to the parent pro- cess, sets errno to indicate the error, and no child process is created. It looks like fork is returning the PID of the child process. Isn't this what you wanted? -- Mike Eager