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 FREEBSD

atf-sh

ATF-SH(1)						    BSD General Commands Manual 						 ATF-SH(1)

NAME

     atf-sh [-s shell] -- interpreter for shell-based test programs

SYNOPSIS

     atf-sh script

DESCRIPTION

     atf-sh is an interpreter that runs the test program given in script after loading the atf-sh(3) library.

     atf-sh is not a real interpreter though: it is just a wrapper around the system-wide shell defined by ATF_SHELL.  atf-sh executes the inter-
     preter, loads the atf-sh(3) library and then runs the script.  You must consider atf-sh to be a POSIX shell by default and thus should not
     use any non-standard extensions.

     The following options are available:

     -s shell	  Specifies the shell to use instead of the value provided by ATF_SHELL.

ENVIRONMENT

     ATF_LIBEXECDIR    Overrides the builtin directory where atf-sh is located.  Should not be overridden other than for testing purposes.
     ATF_PKGDATADIR    Overrides the builtin directory where libatf-sh.subr is located.  Should not be overridden other than for testing purposes.
     ATF_SHELL	       Path to the system shell to be used in the generated scripts.  Scripts must not rely on this variable being set to select a
		       specific interpreter.

EXAMPLES

     Scripts using atf-sh(3) should start with:

	   #! /usr/bin/env atf-sh

     Alternatively, if you want to explicitly choose a shell interpreter, you cannot rely on env(1) to find atf-sh.  Instead, you have to hardcode
     the path to atf-sh in the script and then use the -s option afterwards as a single parameter:

	   #! /path/to/bin/atf-sh -s/bin/bash

ENVIRONMENT

     ATF_SHELL	  Path to the system shell to be used in the generated scripts.

SEE ALSO

     atf-sh(3)

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