Pipe problem Post: 302247305

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Top Forums Programming Pipe problem Post 302247305 by isato on Wednesday 15th of October 2008 11:11:02 AM

10-15-2008

Registered User

Pipe problem

Could anyone tell me whats wrong whit this piping? the commands that they execute are correct. the command I am trying is ls|wc. Both processes go to the right if statement.

Code:

for(i=0;i<argc;i++){
   
       if(i==0&&argc>1){//first command
           if(pipe(pipa1)==-1)
               perror("pipe");
           if((pid=fork())<0)    
                perror("fork");
            if(pid==0){//child
                printf("jag �r f�sta kommandot");
                printf("I am a 1 process--%d, my parent is--%d jag skall exikvera--%s\n ",getpid(),getppid(),com[i].argv[0]);
                dupPipe(pipa1, WRITE_END, STDOUT_FILENO);
                execvp(com[i].argv[0],com[i].argv);
            }                
       }
       if (i>0 && argc==2) {       
         pid = fork();          
         if (pid == 0) {        
            printf("jag �r andra kommandot");
            printf("I am a process--%d, my parent is--%d jag skall exikvera--%s \n ",getpid(),getppid(),com[i].argv[0]);
            dupPipe(pipa1, READ_END, STDIN_FILENO);
            execvp(com[i].argv[0],com[i].argv);
             }
   
        }

Code:

/* Duplicate a pipe to a standard I/O file descriptor, and close both pipe ends
 * Arguments:    pip    the pipe
 *        end    tells which end of the pipe shold be dup'ed; it can be
 *            one of READ_END or WRITE_END
 *        destfd    the standard I/O file descriptor to be replaced
 * Returns:    -1 on error, else destfd
 */
int dupPipe(int pip[2], int end, int destfd){
 
  if (-1 == dup2 (pip[end], destfd))
    {
      perror ("dupPipe()");
      return -1;
    }
  return destfd;
}

isato

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LEARN ABOUT DEBIAN

poe::pipe::oneway

POE::Pipe::OneWay(3pm)					User Contributed Perl Documentation				    POE::Pipe::OneWay(3pm)

NAME

       POE::Pipe::OneWay - a portable API for one-way pipes

SYNOPSIS

	 my ($read, $write) = POE::Pipe::OneWay->new();
	 die "couldn't create a pipe: $!" unless defined $read;

DESCRIPTION

       The right way to create an anonymous pipe varies from one operating system to the next.	Some operating systems support "pipe()".  Others
       require "socketpair()".	And a few operating systems support neither, so a plain old socket must be created.

       POE::Pipe::OneWay will attempt to create a unidirectional pipe using "pipe()", "socketpair()", and IO::Socket::INET, in that order.
       Exceptions are hardcoded for operating systems with broken or nonstandard behaviors.

       The upshot of all this is that an application can portably create a one-way pipe by instantiating POE::Pipe::OneWay.  The work of deciding
       how to create the pipe and opening the handles will be taken care of internally.

       POE::Pipe::OneWay may be used outside of POE, as it doesn't use POE internally.

PUBLIC METHODS

   new [TYPE]
       Create a new one-way pipe, optionally constraining it to a particular TYPE of pipe.  One-way pipes have two ends: a "read" end and a
       "write" end.  On success, new() returns two handles: one for the "read" end and one for the "write" end.  Returns nothing on failure, and
       sets $!	to explain why the constructor failed.

	 my ($read, $write) = POE::Pipe::OneWay->new();
	 die $! unless defined $read;

       TYPE may be one of "pipe", "socketpair", or "inet".  When set, POE::Pipe::OneWay will constrain its search to either "pipe()", a UNIX-
       domain "socketpair()", or plain old sockets, respectively.  Otherwise new() will try each method in order, or a particular method
       predetermined to be the best one for the current operating environment.

BUGS

       POE::Pipe::OneWay may block up to one second on some systems if failure occurs while trying to create "inet" sockets.

SEE ALSO

       POE::Pipe, POE::Pipe::TwoWay.

AUTHOR &; COPYRIGHT
       POE::Pipe::OneWay is copyright 2000-2008 by Rocco Caputo.  All rights reserved.	POE::Pipe::OneWay is free software; you may redistribute
       it and/or modify it under the same terms as Perl itself.

perl v5.14.2							    2012-05-15						    POE::Pipe::OneWay(3pm)

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