Pipe & fifo.... Post: 24785

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Top Forums Programming Pipe & fifo.... Post 24785 by M3xican on Wednesday 17th of July 2002 04:45:19 PM

07-17-2002

Registered User

Pipe & fifo....

Could someone Help me with this code please?

Code:

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>

#define SIZE_B 256      /*buffer's size */
#define NUM_ARG 20      /* max number of args for any command  */

int main()
{
	char *arg1[NUM_ARG];
	char *arg2[NUM_ARG];
	int pippa;	
	pid_t pid1,pid2;
	
	arg1[0]="ls";	/*first command*/
	arg1[1]="-l";
	arg1[2]=0;
	
	arg2[0]="grep";	/*second command*/
	arg2[1]="mishell";
	arg2[2]=0;
	
	mkfifo("./mishell_pipa",S_IRWXU);       /*make fifo*/

        pippa=open("./mishell_pipa",O_RDWR|O_CREAT|O_TRUNC|O_SYNC);    /*get fd*/   

	unlink("./mishell_pipa");       /*unlink file*/

	if(!(pid1=vfork()))	/*first process*/
	{
		dup2(pippa,STDOUT_FILENO);
		execvp(arg1[0],arg1);
		_exit(0);
	}
	else
	{
		waitpid(pid1,NULL,0);	/*wait first process*/
			
		if(!(pid2=vfork()))	/*second process*/
		{
			dup2(pippa,STDIN_FILENO);
			execvp(arg2[0],arg2);
			_exit(0);
		}
		else
			waitpid(pid2,NULL,0);	/*wait second process*/
	return 0;
	}
	
}

I have to create a pipe between 2 process such as the output of the first process
is the input of the second.
In practice I have to do the same thing that the bash does using the follow command:

ls -l|grep mishell

The program works well, but after that grep gives me its output it doesn't come back to
the shell, but stays blocked.

I have tried also to use the mode O_NONBLOCK in the open function, but so the first problem leaves
its place to another. The programm works well, but at the end grep gives me this error:

grep: (standard input): Resource temporarily unavailable

I think that the problem is that grep attend a particular kind of input to terminate, and ls doesn't
give it this input. I've tried to write a EOF in the fifo after the execution of ls, but there
aren't changes.

What can I do????
Help me please!

M3xican

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fssync-debug_stats

FSSYNC-DEBUG_STATS(8)					       AFS Command Reference					     FSSYNC-DEBUG_STATS(8)

NAME

       fssync-debug_stats - Displays various statistics

SYNOPSIS

       fssync-debug stats -cmd <subcommand>
	   [-arg1 <arg1>]
	   [-arg2 <arg2>]
	   [-reason <sync protocol reason code>]
	   [-programtype <program type code>]
	   [-help]

       fssync-debug s -c <subcommand>
	   [-arg1 <arg1>]
	   [-arg2 <arg2>]
	   [-r <sync protocol reason code>]
	   [-p <program type code>]
	   [-h]

DESCRIPTION

       The fssync-debug stats command displays statistics according to the value of the option -cmd.

OPTIONS

       -cmd <subcommand>
	   Specifies statistics subcommand. Available subcommands are:

	   o   pkg    -- general volume package statistics

	   o   vicep  -- vice partition statistics

	   o   hash   -- volume hash chain statistics

	   o   hdr    -- volume header cache statistics

	   o   vlru   -- vlru generation statistics

	   o   help   -- display list of available subcommands

       -arg1 <arg1>
	   Specifies first optional argument, in the context of the chosen subcommand. For vicep statistics, it specifies partition name; for hash
	   statistics, it specifies hash bucket number; for vlru statistics it specifies vlru generation number.

       -arg2 <arg2>
	   Specifies second optional argument, in the context of the chose subcommand. Currently, none of the subcommands use it.

       -reason <sync protocol reason code>
	   Specifies numeric sync protocol reason code.  Available codes are listed in OpenAFS source file src/vol/fssync_inline.h. For
	   SYNC_REASON_NONE, use -reason 0.

       -programtype <program type code>
	   Specifies program type code. Permitted values are fileServer, volumeUtility, salvager, salvageServer, volumeServer and volumeSalvager.

PRIVILEGE REQUIRED

       The issuer must have write access to the file server.  Usually, this means that the issuer must be the local superuser "root" on the file
       server machine.

SEE ALSO

       fssync-debug_header(8), fssync-debug_query(8)

COPYRIGHT

       Copyright 2010 Davor Ocelic <docelic@spinlocksolutions.com>

       This documentation is covered by the IBM Public License Version 1.0.  This man page was written by Davor Ocelic for OpenAFS, based on
       documentation from Steven Jenkins, Tom Keiser and Simon Wilkinson.

OpenAFS 							    2012-03-26						     FSSYNC-DEBUG_STATS(8)

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