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Full Discussion: Help with Mkfifo and exec
Top Forums Programming Help with Mkfifo and exec Post 302469509 by dano88 on Saturday 6th of November 2010 05:15:41 PM
Old 11-06-2010
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);
    }

thanks,
daniel
 

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LEARN ABOUT V7

fork

FORK(2) 							System Calls Manual							   FORK(2)

NAME

       fork  -	spawn new process

SYNOPSIS

       fork( )

DESCRIPTION

       Fork  is  the only way new processes are created.  The new process's core image is a copy of that of the caller of fork.  The only distinc-
       tion is the fact that the value returned in the old (parent) process contains the process ID of the new (child) process,  while	the  value
       returned in the child is 0.  Process ID's range from 1 to 30,000.  This process ID is used by wait(2).

       Files open before the fork are shared, and have a common read-write pointer.  In particular, this is the way that standard input and output
       files are passed and also how pipes are set up.

SEE ALSO

       wait(2), exec(2)

DIAGNOSTICS

       Returns -1 and fails to create a process if: there is inadequate swap space, the user is not super-user and has too many processes, or  the
       system's process table is full.	Only the super-user can take the last process-table slot.

ASSEMBLER

       (fork = 2.)
       sys fork
       (new process return)
       (old process return, new process ID in r0)

       The return locations in the old and new process differ by one word.  The C-bit is set in the old process if a new process could not be cre-
       ated.

																	   FORK(2)
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