[PD] pipes

[david casal]

Hi all,

I'm tinkering with some fuzzy logic code generators, and though they
produce ANSI-C, my skills as a programmer aren't quite up to the job of
making generated code wrap around PD-ways. I thought of maybe doing the
pipe thing, so I wrote (with help from local LUG) the bit of C below...any
advice on how to wrap this in PD? Also, is this something I should be able
to do from within PD, say with 'shell' (and BTW, where -can- I find the
shell object)

cheers,
dc


/* a bit of c to do pipes, by dc
 * bi-pipe.c
 *  -xs
 *
 * practical usage:
 *
 * % bi-pipe 'ls /' 'cat >~/tmp/output'
 * % bi-pipe 'ls /adsadsa' 'cat >~/tmp/output'
 * % bi-pipe -d 'ls /adsadsa' 'cat >~/tmp/output'
 * ls: /adsadsa: No such file or directory
 * %
 */
#include <sys/param.h>

#include <sys/types.h>
#include <sys/socket.h>

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>   /* needed by some glibc versions, remove if trouble */

enum
{
    DEBUG = 0x1
};

void    myerr(int, char *);
void    usage(void);
void    do_half(int, char *);

extern  char  **environ;
        int     flags;

int
main(int argc, char *argv[])
{
    int fd[2], x;

    while ((x = getopt(argc, argv, "dh")) != -1)
    {
        switch (x)
        {
            case 'd':
                flags |= DEBUG;
                break;

            case 'h':
            default:
                usage();
        }
    }

    argc -= optind;
    argv += optind;

    if (argc == 0)
        usage();

    if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd) == -1)
        myerr(1, "pipe");

    switch (fork())
    {
        case -1:
            myerr(1, "fork");

        case 0:
            close(fd[1]);
            do_half(fd[0], argv[0]);
            break;

        default:
            close(fd[0]);
            do_half(fd[1], argv[1]);
            break;
    }

    return 1;
}


void
do_half(int fd, char *prog)
{
    char *argv[4];
    int x;

    if (flags & DEBUG)
        x = 1;
    else
        x = 2;

    for (; x >= 0; x--)
        if (dup2(fd, x) == -1)
            myerr(1, "dup2");

    close(fd);

    argv[0] = "/bin/sh";
    argv[1] = "-c";
    argv[2] = prog;
    argv[3] = NULL;

    execve(argv[0], argv, environ);
    myerr(1, "execve");
}


void
myerr(int status, char *str)
{
    perror(str);
    exit(status);
}


void
usage(void)
{
    fprintf(stderr, "usage: bi-pipe [-d] <cmd one> <cmd two>\n\n");
    exit(1);
}



david casal                   --0+
    ---
d.casal at uea.ac.uk             --9+
    ---
www.ariada.uea.ac.uk/~dcasal  --)+