[프로그래밍] Socket inheritance with fork/dup2/exec

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parent.c

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#include <stdio.h>

#include <stdarg.h>

#include <errno.h>

#include <sys/fcntl.h>

#include <sys/socket.h>

#ifndef STDIN_FILENO

#define STDIN_FILENO 0

#endif

#ifndef STDOUT_FILENO

#define STDOUT_FILENO 1

#endif

#ifndef STDERR_FILENO

#define STDERR_FILENO 2

#endif

void set_blocking(int fd);

void set_nonblocking(int fd);

int main(int argc, char **argv)

{

    int i;

    pid_t pid;

    int to_child_pipe[2];

    int from_child_pipe[2];

    int f_in, f_out, n;

    char buffer[512];

    if (socketpair(AF_UNIX, SOCK_STREAM, 0, to_child_pipe) ||

        socketpair(AF_UNIX, SOCK_STREAM, 0, from_child_pipe) ) {

        fprintf(stderr, "socketpair error (%d)\n", errno);

        exit(1);

    }

    pid = fork();

    if (pid == -1) {

        fprintf(stderr, "fork error (%d)\n", errno);

        exit(1);

    }

    if (pid == 0) { /* CHILD */

        if ( dup2(to_child_pipe[0], STDIN_FILENO) < 0 ||

             close(to_child_pipe[1]) < 0 ||

             close(from_child_pipe[0]) < 0 ||

             dup2(from_child_pipe[1], STDOUT_FILENO) < 0 )

        {

            fprintf(stderr, "dup2/close error (%d)\n", errno);

            exit(1);

        }

        if (to_child_pipe[0] != STDIN_FILENO)

                close(to_child_pipe[0]);

        if (from_child_pipe[1] != STDOUT_FILENO)

                close(from_child_pipe[1]);

        set_blocking(STDIN_FILENO);

        set_nonblocking(STDIN_FILENO);

        execvp(argv[1], &argv[1]);

        fprintf(stderr, "execvp error (%d) on '%s'", errno, argv[1]);

        exit(1);

    }

    /* PARENT */

    if (close(from_child_pipe[1]) < 0 || close(to_child_pipe[0]) < 0) {

        fprintf(stderr, "close error (%d) on child handles", errno);

        exit(1);

    }

    f_in  = from_child_pipe[0];

    f_out = to_child_pipe[1];

    /* read and display data from child process */

    while (1) {

        n = read(f_in, buffer, sizeof(buffer) - 1);

        if (n == 0)

            break;

        if (n == -1) {

            if (errno != ECONNABORTED && errno != ECONNRESET)

                fprintf(stderr, "read error (%d)\n", errno);

            break;

        }

        buffer[n] = '\0';

        printf("%s", buffer);

        fflush(NULL);

    }

    exit(1);

}

void set_blocking(int fd)

{

    int val;

    if ((val = fcntl(fd, F_GETFL, 0)) == -1)

        return;

    if (val & O_NONBLOCK) {

        val &= ~O_NONBLOCK;

        fcntl(fd, F_SETFL, val);

    }

}

void set_nonblocking(int fd)

{

    int val;

    if ((val = fcntl(fd, F_GETFL, 0)) == -1)

        return;

    if (!(val & O_NONBLOCK)) {

        val |= O_NONBLOCK;

        fcntl(fd, F_SETFL, val);

    }

}

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child.c

-------

#include <stdio.h>

#include <Windows.h>

void ErrorExit(LPTSTR lpszFunction);

main(int argc, char **argv)

{

    char str[] = "hello";

    int i;

    DWORD btw = (DWORD)strlen(str);

    DWORD bw;

    STARTUPINFO si;

    OVERLAPPED ol;

    HANDLE hStdout;

    ZeroMemory(&ol, sizeof(ol));

    hStdout = GetStdHandle(STD_OUTPUT_HANDLE);

    for (i=0; i<5; i++) {

        if (! WriteFile(hStdout, str, btw, &bw, &ol) ) {

            ErrorExit("WriteFile");

            exit(1);

        }

        Sleep(1000);

    }

}

void ErrorExit(LPTSTR lpszFunction)

{

    LPVOID lpMsgBuf;

    DWORD dw = GetLastError();

    FormatMessage(

        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,

        NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),

        (LPTSTR) &lpMsgBuf, 0, NULL );

    fprintf(stderr, "%s error (%d): %s\n", lpszFunction, dw, lpMsgBuf);

    ExitProcess(dw);

}

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