Help with Mkfifo and exec


 
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# 1  
Old 11-07-2010
Help with Mkfifo and exec

Hello guys!

I am doing a project for the university and I have to do that a process has to create several children through fork(). The father process sends a pathname to each one through exec and the children must send to the father a list with the files from each directory.

The father is waiting and the children don't send anything. I must to do the pipe with mkfifo. I am trying to send text from the children but nothing happens. This is the code that I have wroten:



Code:
struct stat buf;
 mkfifo(NOMBREFIFO, S_IRWXU);
    while (--argc>0){
        stat (argv[argc], &buf);
        if (S_ISDIR(buf.st_mode)){
            pid = fork();
            
            if (pid<0) fprintf (stderr, "error %d", errno); 
            if (pid==0) printf ("hhhhhhhhh");
            if (pid==0 && (exec=execl ("./listarordenado", argv[argc], NULL))<0) fprintf (stderr, "error %d", errno);
            if (pid>0 && wait(&status) && waitpid (pid, &status, 0)){
                printf ("ssssssssss");
                 while(TRUE) {
                      fp=open(NOMBREFIFO,O_RDONLY);
                      nbytes=read(fp,buffer,TAM_BUF-1);
                      buffer[nbytes]='\0';
                      printf("%d Cadena recibida: %s \n",i, buffer);
                      close(fp);
                      i++;
                }
                 }
         }
      } 


/////***code of listarordenado*//


for (i=0; i<50; i++){
        if ((fp=open(NOMBREFIFO,O_WRONLY))==-1)
            perror("fopen");
          else {    
                descr=write(fp,argv[1],strlen(argv[1]));
        }
         
      close(fp);
    }

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):

University: Universidad de Castilla-La Mancha (Ciudad Real, spain)
Professor: Carlos Gonzalez Morcillo :: Personal Web Page www. inf-cr.uclm.es/www/cglez/
Degree: "Computer engineering"
Subject: "Ampliación de Sistemas Operativos" + info: www. esi.uclm.es:8081/www/GuiaDocente/GuiaDocente0910/guias/42534_0910.pdf
# 2  
Old 11-07-2010
Playing with the named pipe on the shell first is instructional (mknod path p). One party needs to be opening to read before one opens to write or one read may get many write. There is no wait, just blocking. Beware ccc>pipe as your login hangs, do (xxx >pipe)& after (yyy <pipe)&.

Named pipes are more a client-server or shell thing, as pipe() suffices for fork()/exec(), and popen() makes life simpler.

Last edited by DGPickett; 11-07-2010 at 06:37 AM..
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