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Full Discussion: Help with Mkfifo and exec
Homework and Emergencies Homework & Coursework Questions Help with Mkfifo and exec Post 302469573 by dano88 on Sunday 7th of November 2010 03:28:18 AM
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
 

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MKFIFO(3)						     Linux Programmer's Manual							 MKFIFO(3)

NAME
mkfifo - make a FIFO special file (a named pipe) SYNOPSIS
#include <sys/types.h> #include <sys/stat.h> int mkfifo(const char *pathname, mode_t mode); DESCRIPTION
mkfifo makes a FIFO special file with name pathname. mode specifies the FIFO's permissions. It is modified by the process's umask in the usual way: the permissions of the created file are (mode & ~umask). A FIFO special file is similar to a pipe, except that it is created in a different way. Instead of being an anonymous communications chan- nel, a FIFO special file is entered into the file system by calling mkfifo. Once you have created a FIFO special file in this way, any process can open it for reading or writing, in the same way as an ordinary file. However, it has to be open at both ends simultaneously before you can proceed to do any input or output operations on it. Opening a FIFO for reading normally blocks until some other process opens the same FIFO for writing, and vice versa. See fifo(4) for non-blocking handling of FIFO special files. RETURN VALUE
The normal, successful return value from mkfifo is 0. In the case of an error, -1 is returned (in which case, errno is set appropriately). ERRORS
EACCES One of the directories in pathname did not allow search (execute) permission. EEXIST pathname already exists. ENAMETOOLONG Either the total length of pathname is greater than PATH_MAX, or an individual file name component has a length greater than NAME_MAX. In the GNU system, there is no imposed limit on overall file name length, but some file systems may place limits on the length of a component. ENOENT A directory component in pathname does not exist or is a dangling symbolic link. ENOSPC The directory or filesystem has no room for the new file. ENOTDIR A component used as a directory in pathname is not, in fact, a directory. EROFS pathname refers to a read-only filesystem. CONFORMING TO
POSIX.1 SEE ALSO
mkfifo(1), read(2), write(2), open(2), close(2), stat(2), umask(2), fifo(4) Linux 1.2.13 1995-09-03 MKFIFO(3)
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