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#ifndef lint
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static const char RCSid[] = "$Id: unix_process.c,v 3.7 2005/01/20 04:08:00 greg Exp $";
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#endif
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/*
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* Routines to communicate with separate process via dual pipes
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* Unix version
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*
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* External symbols declared in standard.h
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*/
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#include "copyright.h"
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include "rtprocess.h"
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#include "rtio.h"
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int
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open_process( /* open communication to separate process */
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SUBPROC *pd,
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char *av[]
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)
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{
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char *compath;
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int p0[2], p1[2];
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pd->running = 0; /* not yet */
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/* find executable */
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compath = getpath(av[0], getenv("PATH"), 1);
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if (compath == 0)
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return(0);
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if (pipe(p0) < 0 || pipe(p1) < 0)
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return(-1);
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if ((pd->pid = fork()) == 0) { /* if child */
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close(p0[1]);
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close(p1[0]);
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if (p0[0] != 0) { /* connect p0 to stdin */
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dup2(p0[0], 0);
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close(p0[0]);
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}
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if (p1[1] != 1) { /* connect p1 to stdout */
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dup2(p1[1], 1);
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close(p1[1]);
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}
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execv(compath, av); /* exec command */
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perror(compath);
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_exit(127);
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}
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if (pd->pid == -1)
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return(-1);
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close(p0[0]);
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close(p1[1]);
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pd->r = p1[0];
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pd->w = p0[1];
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/*
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* Close write stream on exec to avoid multiprocessing deadlock.
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* No use in read stream without it, so set flag there as well.
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* GW: This bug took me two days to figure out!!
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*/
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fcntl(pd->r, F_SETFD, FD_CLOEXEC);
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fcntl(pd->w, F_SETFD, FD_CLOEXEC);
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pd->running = 1;
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return(PIPE_BUF);
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}
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int
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close_process( /* close pipes and wait for process */
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SUBPROC *pd
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)
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{
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int status;
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if (!pd->running)
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return(0);
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close(pd->r);
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close(pd->w);
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pd->running = 0;
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if (waitpid(pd->pid, &status, 0) == pd->pid)
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return(status>>8 & 0xff);
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return(-1); /* ? unknown status */
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}
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