using pipe in a loop Post: 94710

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Top Forums Programming using pipe in a loop Post 94710 by netman on Tuesday 3rd of January 2006 08:57:27 AM

01-03-2006

Registered User

Hi

thanks for your attention

here I have written a sample code that works
only for one time I mean if I ommit the line exit(EXIT_SUCCESS) in default part the activity of
client never ends with the wrong output it means that only it printfs:

child: the name is %s !!

for unlimited times but when I use this line every thing is ok but just for one data just for
"afi" in array names and then every thing ends.

well what do you think about it ? what is my problem?

one another time thanks for your attention

Best Regards.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <wait.h>

static void sigchld_handler(int sig) { int stat; wait(&stat); }

int main()
{

char names[7][10]={"afi","shin","pedi","arin","nazin","mam","bab"};
int fd[2];
int nread;
int i,j,rc;
pid_t pid;
char buf[1024];

struct sigaction sigchldr;
memset(&sigchldr, 0, sizeof(struct sigaction));
sigchldr.sa_handler = sigchld_handler; sigaction(SIGCHLD, &sigchldr, NULL);

printf("\n start");

if ((rc=pipe(fd))<0)
{
printf("\n pipe error");
exit(0);
}

i=0;
while(i<7)
{

printf("\n enter while %d",i);

switch((pid=fork()))
{

case -1:

printf("\n fork error");
exit(EXIT_FAILURE);

case 0: //child

printf("\n child");
close(fd[1]);
while((nread=read(fd[0],buf,1024)!=0))
{
char c=getchar();

printf("\n child: the name is %s !!",buf);
}
close(fd[0]);
exit(EXIT_SUCCESS);

default: //parent

printf("\n parent");
char c=getchar();

close(fd[0]);
printf("\n strart parent %s",names[i]);
write(fd[1],names[i],1024);
printf("\n writing %s is finished $",names[i]);
close(fd[1]);
exit(EXIT_SUCCESS);

}
i++;
}
exit(EXIT_SUCCESS);
}

netman

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bsd_signal

BSD_SIGNAL(3P)						     POSIX Programmer's Manual						    BSD_SIGNAL(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       bsd_signal - simplified signal facilities

SYNOPSIS

       #include <signal.h>

       void (*bsd_signal(int sig, void (*func)(int)))(int);

DESCRIPTION

       The bsd_signal() function provides a partially compatible interface for programs written to historical system interfaces  (see  APPLICATION
       USAGE).

       The function call bsd_signal(sig, func) shall be equivalent to the following:

	      void (*bsd_signal(int sig, void (*func)(int)))(int)
	      {
		  struct sigaction act, oact;

		  act.sa_handler = func;
		  act.sa_flags = SA_RESTART;

		  sigemptyset(&act.sa_mask);
		  sigaddset(&act.sa_mask, sig);
		  if (sigaction(sig, &act, &oact) == -1)
		      return(SIG_ERR);

		  return(oact.sa_handler);
	      }

       The handler function should be declared:

	      void handler(int sig);

       where sig is the signal number. The behavior is undefined if func is a function that takes more than one argument, or an argument of a dif-
       ferent type.

RETURN VALUE

       Upon successful completion, bsd_signal() shall return the previous action for sig. Otherwise, SIG_ERR shall be returned and errno shall	be
       set to indicate the error.

ERRORS

       Refer to sigaction().

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       This  function  is  a direct replacement for the BSD signal() function for simple applications that are installing a single-argument signal
       handler function. If a BSD signal handler function is being installed that expects more than one argument, the application has to be  modi-
       fied  to  use sigaction(). The bsd_signal() function differs from signal() in that the SA_RESTART flag is set and the SA_RESETHAND is clear
       when bsd_signal() is used. The state of these flags is not specified for signal().

       It is recommended that new applications use the sigaction() function.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       sigaction(), sigaddset(), sigemptyset(), signal(), the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003							    BSD_SIGNAL(3P)