src/common/unix_process.c

#ifndef lint
static const char       RCSid[] = "$Id: unix_process.c,v 3.9 2009/12/12 23:08:13 greg Exp $";
#endif
/*
 * Routines to communicate with separate process via dual pipes
 * Unix version
 *
 * External symbols declared in standard.h
 */

#include "copyright.h"

#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <stdlib.h>

#include "rtprocess.h"
#include "rtio.h"


int
open_process(           /* open communication to separate process */
SUBPROC *pd,
char    *av[]
)
{
        char    *compath;
        int     p0[2], p1[2];

        pd->running = 0;                /* not going yet */
        
        if (av == NULL)                 /* cloning operation? */
                compath = NULL;
        else if ((compath = getpath(av[0], getenv("PATH"), X_OK)) == NULL)
                return(0);
        if (pipe(p0) < 0 || pipe(p1) < 0)
                return(-1);
        if ((pd->pid = fork()) == 0) {  /* if child... */
                close(p0[1]);
                close(p1[0]);
                if (p0[0] != 0) {       /* connect p0 to stdin */
                        dup2(p0[0], 0);
                        close(p0[0]);
                }
                if (p1[1] != 1) {       /* connect p1 to stdout */
                        dup2(p1[1], 1);
                        close(p1[1]);
                }
                if (compath == NULL)    /* just cloning? */
                        return(0);
                execv(compath, av);     /* else exec command */
                perror(compath);
                _exit(127);
        }
        if (pd->pid == -1)
                return(-1);
        close(p0[0]);
        close(p1[1]);
        pd->r = p1[0];
        pd->w = p0[1];
        /*
         * Close write stream on exec to avoid multiprocessing deadlock.
         * No use in read stream without it, so set flag there as well.
         * GW: This bug took me two days to figure out!!
         */
        fcntl(pd->r, F_SETFD, FD_CLOEXEC);
        fcntl(pd->w, F_SETFD, FD_CLOEXEC);
        pd->running = 1;
        return(PIPE_BUF);
}


int
close_process(          /* close pipes and wait for process */
SUBPROC *pd
)
{
        int     status;

        if (!pd->running)
                return(0);
        close(pd->w);
        close(pd->r);
        pd->running = 0;
        if (waitpid(pd->pid, &status, 0) == pd->pid)
                return(status>>8 & 0xff);

        return(-1);             /* ? unknown status */
}


Revision:	3.10
Committed:	Thu Jun 14 05:13:25 2012 UTC (11 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad4R2P2, rad5R0, rad4R2, rad4R2P1
Changes since 3.9:	+13 -10 lines
Log Message:	Simplified creation of child process
#	User	Rev	Content
1	schorsch	3.1	#ifndef lint
2	greg	3.10	static const char RCSid[] = "$Id: unix_process.c,v 3.9 2009/12/12 23:08:13 greg Exp $";
3	schorsch	3.1	#endif
4			/*
5			* Routines to communicate with separate process via dual pipes
6			* Unix version
7			*
8			* External symbols declared in standard.h
9			*/
10
11			#include "copyright.h"
12	schorsch	3.2
13			#include <sys/types.h>
14			#include <sys/wait.h>
15	greg	3.6	#include <fcntl.h>
16	greg	3.7	#include <stdlib.h>
17	schorsch	3.1
18			#include "rtprocess.h"
19	greg	3.7	#include "rtio.h"
20	schorsch	3.1
21
22			int
23			open_process( /* open communication to separate process */
24			SUBPROC *pd,
25			char *av[]
26			)
27			{
28			char *compath;
29			int p0[2], p1[2];
30
31	greg	3.10	pd->running = 0; /* not going yet */
32
33			if (av == NULL) /* cloning operation? */
34			compath = NULL;
35			else if ((compath = getpath(av[0], getenv("PATH"), X_OK)) == NULL)
36	schorsch	3.1	return(0);
37			if (pipe(p0) < 0 \|\| pipe(p1) < 0)
38			return(-1);
39	greg	3.10	if ((pd->pid = fork()) == 0) { /* if child... */
40	schorsch	3.1	close(p0[1]);
41			close(p1[0]);
42			if (p0[0] != 0) { /* connect p0 to stdin */
43			dup2(p0[0], 0);
44			close(p0[0]);
45			}
46			if (p1[1] != 1) { /* connect p1 to stdout */
47			dup2(p1[1], 1);
48			close(p1[1]);
49			}
50	greg	3.10	if (compath == NULL) /* just cloning? */
51			return(0);
52			execv(compath, av); /* else exec command */
53	schorsch	3.1	perror(compath);
54			_exit(127);
55			}
56			if (pd->pid == -1)
57			return(-1);
58			close(p0[0]);
59			close(p1[1]);
60			pd->r = p1[0];
61			pd->w = p0[1];
62	greg	3.6	/*
63			* Close write stream on exec to avoid multiprocessing deadlock.
64			* No use in read stream without it, so set flag there as well.
65			* GW: This bug took me two days to figure out!!
66			*/
67			fcntl(pd->r, F_SETFD, FD_CLOEXEC);
68			fcntl(pd->w, F_SETFD, FD_CLOEXEC);
69	schorsch	3.1	pd->running = 1;
70			return(PIPE_BUF);
71			}
72
73
74
75			int
76			close_process( /* close pipes and wait for process */
77			SUBPROC *pd
78			)
79			{
80	schorsch	3.8	int status;
81	schorsch	3.1
82	greg	3.5	if (!pd->running)
83			return(0);
84	schorsch	3.1	close(pd->w);
85	greg	3.10	close(pd->r);
86	schorsch	3.1	pd->running = 0;
87	greg	3.10	if (waitpid(pd->pid, &status, 0) == pd->pid)
88	greg	3.5	return(status>>8 & 0xff);
89	greg	3.10
90	schorsch	3.1	return(-1); /* ? unknown status */
91			}
92
93