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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 CENTOS

nsenter

NSENTER(1)							   User Commands							NSENTER(1)

NAME

       nsenter - run program with namespaces of other processes

SYNOPSIS

       nsenter [options] [program] [arguments]

DESCRIPTION

       Enters the namespaces of one or more other processes and then executes the specified program.  Enterable namespaces are:

       mount namespace
	      mounting	and unmounting filesystems will not affect rest of the system (CLONE_NEWNS flag), except for filesystems which are explic-
	      itly marked as shared (by mount --make-shared).  See /proc/self/mountinfo for the shared flag.

       UTS namespace
	      setting hostname, domainname will not affect rest of the system (CLONE_NEWUTS flag).

       IPC namespace
	      process will have independent namespace for System V message queues, semaphore sets and shared memory segments (CLONE_NEWIPC flag).

       network namespace
	      process will have independent IPv4 and IPv6 stacks, IP routing tables, firewall rules, the /proc/net  and  /sys/class/net  directory
	      trees, sockets etc.  (CLONE_NEWNET flag).

       PID namespace
	      children	will  have  a  set of PID to process mappings separate from the nsenter process (CLONE_NEWPID flag).  nsenter will fork by
	      default if changing the PID namespace, so that the new program and its children share the same PID namespace and are visible to each
	      other.  If --no-fork is used, the new program will be exec'ed without forking.

       See the clone(2) for exact semantics of the flags.

       If program is not given, run ``${SHELL}'' (default: /bin/sh).

OPTIONS

       Argument  with  square brakets, such as [file], means optional argument.  Command line syntax to specify optional argument --mount=/path/to
       /file.  Please notice the equals sign.

       -t, --target pid
	      Specify a target process to get contexts from.  The paths to the contexts specified by pid are:

	      /proc/pid/ns/mnt	  the mount namespace
	      /proc/pid/ns/uts	  the UTS namespace
	      /proc/pid/ns/ipc	  the IPC namespace
	      /proc/pid/ns/net	  the network namespace
	      /proc/pid/ns/pid	  the PID namespace
	      /proc/pid/root	  the root directory
	      /proc/pid/cwd	  the working directory respectively

       -m, --mount [file]
	      Enter the mount namespace.  If no file is specified enter the mount namespace of the target process.  If file is specified enter the
	      mount namespace specified by file.

       -u, --uts [file]
	      Enter the UTS namespace.	If no file is specified enter the UTS namespace of the target process.	If file is specified enter the UTS
	      namespace specified by file.

       -i, --ipc [file]
	      Enter the IPC namespace.	If no file is specified enter the IPC namespace of the target process.	If file is specified enter the IPC
	      namespace specified by file.

       -n, --net [file]
	      Enter the network namespace.  If no file is specified enter the network namespace of the target process.	If file is specified enter
	      the network namespace specified by file.

       -p, --pid [file]
	      Enter the PID namespace.	If no file is specified enter the PID namespace of the target process.	If file is specified enter the PID
	      namespace specified by file.

       -r, --root [directory]
	      Set the root directory.  If no directory is specified set the root directory to the root directory of the target process.  If direc-
	      tory is specified set the root directory to the specified directory.

       -w, --wd [directory]
	      Set the working directory.  If no directory is specified set the working directory to the working directory of the  target  process.
	      If directory is specified set the working directory to the specified directory.

       -F, --no-fork
	      Do not fork before exec'ing the specified program.  By default when entering a pid namespace enter calls fork before calling exec so
	      that the children will be in the newly entered pid namespace.

       -V, --version
	      Display version information and exit.

       -h, --help
	      Print a help message.

SEE ALSO

       setns(2), clone(2)

AUTHOR

       Eric Biederman <ebiederm@xmission.com>

AVAILABILITY

       The nsenter command is part of the util-linux package and is available  from  Linux  Kernel  Archive  <ftp://ftp.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux							   January 2013 							NSENTER(1)
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