Threaded Mode | Linear Mode

codecaine · 02-02-2010, 04:27 PM

This program writes to the sort program then pipe the data back into the program to read it instead of the standard output.

Code:

#include <string>

#include <iostream>

#include <sys/types.h>

#include <sys/wait.h>

#include <sys/uio.h>

#include <unistd.h>

#define MAXSTRS 5

using namespace std;

int main(void)

{

        int     child_in[2], child_out[2], nbytes;

        pid_t   childpid;

        string strings[MAXSTRS] = { "echo\n", "bravo\n", "alpha\n",

                                  "charlie\n", "delta\n"};

        char buffer[255];

        pipe(child_in);

    pipe(child_out);

    childpid = fork();

        if(childpid != 0)

        {

        close(child_in[0]); // read end of the pipe isnt used in this process

        close(child_out[1]); //write end isnt used here

        for(int i = 0; i < MAXSTRS; i++)

        {

            write(child_in[1], strings[i].c_str(), strings[i].size());

        }

        close(child_in[1]); //so sort gets to EOF

        //sort will finish reading here then sort and send the results to the child_out pipe

        int line = 0;

        FILE *test = fdopen(child_out[0],"r");

        while(fgets(buffer,sizeof(buffer),test) != 0)

        {

            //replace this code that loads the stuff into an array

            line++;

            cout<<line<<". "<<buffer;

        }

        wait(NULL);

        }

        else

        {

        close(child_in[1]); // write end of the pipe isnt used in this process

        close(child_out[0]); //read end isnt used here

        dup2(child_in[0], 0);

        dup2(child_out[1], 1);

                execlp("sort", "sort", NULL);

        }

        return(0);

}

***drdebcol*** · 02-02-2010, 07:19 PM

Great code. You used really good libs there !

codecaine · (This post was last modified: 02-03-2010 12:24 AM by codecaine.)

You that is just a small look at unix api Smile

It is very powerful windows have nothing like it to pipe data. free pascal compiler has full access to unix api also