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Full Discussion: Piping Question
Top Forums Programming Piping Question Post 302189048 by mtobin1987 on Thursday 24th of April 2008 11:24:19 PM
Old 04-25-2008
Piping Question

I have a piping question, I am trying to implement piping on my own shell and am having some trouble...esentially I am trying to make something to do command|command|command.
I can get it to work fine if the last pipe command is not forked, but executes in the shell and then exits..but I need it to fork. I tryed the following, but it will hang..any suggestions? I have a feeling it has something to do with closing/opening descriptors but i don't know...thanks.:
Code:
int pipe1[2], pipe2[2];

        pipe(pipe1);//create first pipe
		pid_t PID=fork();
        if(PID==0){
                close(1);
                dup(pipe1[1]);
                close(pipe1[0]);
                close(pipe1[1]);
               	execvp(*argv,argv);
                printf("operation failed");

        } else {
                
                pipe(pipe2);
				pid_t PID2=fork();
                if (PID2==0) {
                        close(0);
                        dup(pipe1[0]);
                        close(1);
                        dup(pipe2[1]);
                        close(pipe1[0]);
                        close(pipe1[1]);
                        close(pipe2[0]);
                        close(pipe2[1]);
                        execvp(*argv2, argv2);
                } else {
                		pid_t PID3=fork();
   				waitpid(PID3,&status,0);<-----Not sure about this
                		if(PID3==0){
                        close(0);
                        dup(pipe2[0]);
                        close(pipe1[0]);
                        close(pipe1[1]);
                        close(pipe2[0]);
                        close(pipe2[1]);
                        execvp(*argv3, argv3);
                		}
                		
                	}
      	  }


Last edited by Yogesh Sawant; 04-25-2008 at 04:33 AM.. Reason: added code tags
 

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GIT-PACK-REDUNDANT(1)						    Git Manual						     GIT-PACK-REDUNDANT(1)

NAME
git-pack-redundant - Find redundant pack files SYNOPSIS
git pack-redundant [ --verbose ] [ --alt-odb ] < --all | .pack filename ... > DESCRIPTION
This program computes which packs in your repository are redundant. The output is suitable for piping to xargs rm if you are in the root of the repository. git pack-redundant accepts a list of objects on standard input. Any objects given will be ignored when checking which packs are required. This makes the following command useful when wanting to remove packs which contain unreachable objects. git fsck --full --unreachable | cut -d ' ' -f3 | git pack-redundant --all | xargs rm OPTIONS
--all Processes all packs. Any filenames on the command line are ignored. --alt-odb Don't require objects present in packs from alternate object directories to be present in local packs. --verbose Outputs some statistics to stderr. Has a small performance penalty. SEE ALSO
git-pack-objects(1) git-repack(1) git-prune-packed(1) GIT
Part of the git(1) suite Git 1.7.10.4 11/24/2012 GIT-PACK-REDUNDANT(1)
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