When I am writing my own interpreter... Post: 302142174

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Top Forums Programming When I am writing my own interpreter... Post 302142174 by Legend986 on Wednesday 24th of October 2007 11:01:06 PM

10-25-2007

Registered User

Hmm... I seem to be doing something wrong. Here's what I've been doing...

Code:

I'm creating a filedescriptor fd[2]
fork child1
if(pid1 == 0) {
        close(fd[1]); 
        setting fd[0] to STDIN_FILENO using dup2
         close(fd[0]);
        }
        execlp("wc","wc",(char *) 0);
    }
    else {
        fork child 2
        if(pid2 == 0) {
               close(fd[1]);  
               set fd[0] to STDIN_FILENO using dup2
               close(fd[0]);
               set fd[1] to STDOUT_FILENO using dup2
               close(fd[1]);
               execlp("wc","wc", (char *) 0);
        }
        else {
            //parent continues
            fork child 3
            if(pid3 == 0) {
                    close(fd[0]);
                    set fd[1] to STDOUT_FILENO using dup2
                    close(fd[1])
                    execlp("ls","-la", (char *) 0);
            }
        }

What I'm trying to do here is creating a two level pipe for the command: ls -la | wc | wc

It works upto one level but after that I'm getting an "dup2: Bad File Descriptor" error maybe because of the child 2... I'm not sure what mistake I'm doing... Any suggestions on how to get around this one?

Last edited by Legend986; 10-25-2007 at 12:08 AM..

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LEARN ABOUT DEBIAN

binfmtcxx-interpreter

binfmtcxx(1)							     binfmt_C							      binfmtcxx(1)

NAME

       binfmtcxx-interpreter - binfmt_misc C++ handler

SYNOPSIS

       binfmtcxx-interpreter C++-source-file-name [command-line opions ...]

DESCRIPTION

       binfmtcxx-interpreter compiles a C++ source file specified on the command-line using C++ compiler, and executes the resulting file.

       It  is  designed  to be used as a handler for binfmt_misc handler, which is a system used in Linux for handling arbitrary files as executa-
       bles.

       The command-line options are passed on to the compiled binary.

FILE MAGIC

       There is a requirement for C++ source files to have the magic characters /*BINFMTCXX: at the beginning of the file.

       That line also is used to specify the additional command-line options for C++ compiler.

ENVIRONMENT

       GXX    The compiler used.  The default is to use g++

       CXX    The compiler used, if GXX variable is not set.

	      Will fall back to using GCC and CC

       BINFMTCTMPDIR

	      Temporary directory used for binary and execution.

	      Falls back to $TMPDIR $TEMPDIR or /tmp

       BINFMTC_DEBUG
	      enables debug output if set.

       BINFMTCXX_GXX_OPTS
	      Additional G++ options.  Use BINFMTC_DEBUG to verify the options being passed on to g++.

	      The default is  -O0 -Wall -g

AUTHOR

       Junichi Uekawa (dancer@debian.org)

       Upstream page is available at http://www.netfort.gr.jp/~dancer/software/

SEE ALSO

       binfmtasm-interpreter(1), binfmtc-interpreter(1), binfmtcxx-interpreter(1),  binfmtf-interpreter(1),  binfmtf95-interpreter(1),	binfmtgcj-
       interpreter(1)

binfmt_misc Dancer						    2009 Feb 8							      binfmtcxx(1)