From: Kikutani Makoto <kikutani@...>
Date: 1997-11-11T00:09:12+09:00
Subject: [ruby-list:5243] read from subprocess


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きくたにです。

前にもちょっと書いたことがありますが、添付1のC programを
走らせて、子プロセスの添付2のrubyスクリプトが文字列"ruby"を
受け取らないのはなぜでしょう？

似たようなことをPythonでやると添付の3番目で動くのですけど。

-- 
人生を背負い投げ

菊谷 誠(Kikutani Makoto)  kikutani@eis.or.jp hgf03701@niftyserve.or.jp
                          http://www.eis.or.jp/muse/kikutani/

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

main()
{
   int pid, i, slen, l;
   char *cmd, *arg0, arg1[8], *str;
   int channel[2]; /* IPC channel with child process */
   char buf[10];

   if (socketpair(AF_UNIX, SOCK_STREAM, 0, channel) < 0) {
      fprintf(stderr, "socketpair failed\n");
      return;
   }

   if ((pid = vfork()) == -1) {
      return;
   }

   if (pid == 0) {		/* child process */
#if 0
      cmd = "./ipc0";
      arg0 = "ipc0";
#else
      cmd = "./ipc0.rb";
      arg0 = "ipc0.rb";
#endif
      sprintf(arg1, "%d", channel[0]);
      execl(cmd, arg0, arg1, NULL);
      perror("execl failed");
      close( channel[0] );
      _exit( 1 );
   }

   /* parent process */	
   close(channel[0]);


   i = 0x12345678;
   if ((l = write( channel[1], &i, sizeof(int))) != sizeof(int))
     printf("ipc-test0.c: int write failed. written length =  %d\n", l);

   if ((l = read( channel[1], buf, 2)) != 2)
     printf("ipc-test0.c: int read failed. read length =  %d\n", l);
   printf("buf = %s\n", buf);

   str = "ruby";
   slen = strlen(str);
   fflush(stdout);
   if ((l = write( channel[1], str, slen)) != slen)
     printf("ipc-test0.c: str write failed. written length =  %d\n", l);
   if ((l = read( channel[1], buf, 2)) != 2)
     printf("ipc-test0.c: int read failed. read length =  %d\n", l);
   printf("buf = %s\n", buf);

}

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#!/usr/bin/python
import sys,os,string

def read_int(fd):
    i = fd.read(4)
    v = ord(i[3])
    v = v * 256 + ord(i[2])
    v = v * 256 + ord(i[1])
    v = v * 256 + ord(i[0])
    return v

port = string.atoi(sys.argv[1])
sys.stderr.write("port = " + sys.argv[1] + "\n")

fd = os.fdopen(port, "r+")
i = read_int(fd)
sys.stderr.write("i = %x\n" % i)
fd.write("OK")

line = fd.read(4)
sys.stderr.write("line = " + line + "\n")
fd.write("OK")

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