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/*
* Copyright (c) 1990 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND CARNEGIE MELLON UNIVERSITY
* DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT
* SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
* RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
* CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Users of this software agree to return to Carnegie Mellon any
* improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*
* Export of this software is permitted only after complying with the
* regulations of the U.S. Deptartment of Commerce relating to the
* Export of Technical Data.
*/
#include <c.h>
/*
* This routine does a double fork so that the (grand)child won't
* hang on exit because the (grand)parent never wait(2)ed for it.
* Note: grandchild will be inherited by init (proc 1) on exit.
**********************************************************************
* HISTORY
* $Log: dfork.c,v $
* Revision 1.2 90/12/11 17:51:32 mja
* Add copyright/disclaimer for distribution.
*
* 30-Apr-85 Steven Shafer (sas) at Carnegie-Mellon University
* Adapted for 4.2 BSD UNIX. Inserted READ and WRITE macros here
* rather than using <modes.h>, which is obsolete.
*
* 13-Mar-85 Glenn Marcy (gm0w) at Carnegie-Mellon University
* Made code more careful about closing pipes in cases of system
* call failures.
*
*/
#define READ 0
#define WRITE 1
dfork() {
int pid;
int fildes[2];
if (pipe(fildes) == CERROR)
return(CERROR);
if ((pid = fork()) == CERROR) {
close(fildes[READ]);
close(fildes[WRITE]);
return(CERROR);
}
if (pid) {
close(fildes[WRITE]);
while (wait(0) != pid);
if (read(fildes[READ], &pid, sizeof(int)) != sizeof(int))
pid = CERROR;
close(fildes[READ]);
return(pid);
} else {
close(fildes[READ]);
if ((pid = fork()) == CERROR)
exit(CERROR);
if (pid) {
write(fildes[WRITE], &pid, sizeof(int));
close(fildes[WRITE]);
exit(0);
}
close(fildes[WRITE]);
return(0);
}
}
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