Programming

# include <stdio.h>
# include <iostream>

using namespace std;

int
main(int argc, char * argv[])
{

	string file_list = "";
   	string search_string = "a";

        file_list = "/home/vivekv/input_file-2.txt";	// file contains 7366 lines of character a (one char only for each line)

  	string query_string = "grep -nr " + search_string + " " + file_list + " | awk -F: '{printf \"%s %s\", $1 \" -\", $2 \" \\n\"}' ";

   	system(query_string.c_str());

 	exit(0);
}

# include <stdio.h>
# include <iostream>
# include <signal.h>
# include <sys/wait.h>

# define MAXLINE        100000


using namespace std;

int
main(int argc, char * argv[])
{
        int inpipe[2];
        pid_t pid;
        pid_t child_pid;

        if (  pipe(inpipe) < 0 )
        {
                cerr << "PIPE ERROR" << endl;
                return -2;
        }
        if ( (pid = fork()) < 0 )
        {
                cerr << "FORK ERROR" << endl;
                return -3;
        }
        else if (pid == 0)   // CHILD PROCESS
        {
                child_pid = getpid();
                cout << endl << endl << "INSIDE CHILD:-----> pid = " << child_pid << endl << endl;

                close(inpipe[0]);

                if (inpipe[1] != STDOUT_FILENO)
                {
                        if (dup2(inpipe[1], STDOUT_FILENO) != STDOUT_FILENO)
                        {
                                cerr << "dup2 error to stdout" << endl;
                        }

                        execl("/home/vivekv/dfs-fm-1.0.0/dfs-zgrep", "dfs-zgrep", NULL );

                        close(inpipe[1]);
                }


                return 0;
        }
        else    // PARENT PROCESS
        {
                // sleep(5);

                cout << endl << endl << "INSIDE PARENT: waiting for " << pid << " to finish " << endl << endl;

                cout << endl << endl << "CHILD: -----> child_pid = " << child_pid << endl << endl;
                cout << endl << endl << "PARENT:-----> pid = " << pid << endl << endl;

                // waitpid(child_pid, 0, 0);

                int rv;
                char line[MAXLINE];
                close(inpipe[1]);


                if ( (rv = read(inpipe[0], line, MAXLINE)) < 0 )
                {
                        cerr << "READ ERROR FROM PIPE" << endl;
                }
                else if (rv == 0)
                {
                        cerr << "Child Closed Pipe" << endl;
                        return 0;
                }
                cout << endl << endl << "INSIDE PARENT PROCESS...." << endl << line << endl;

                close(inpipe[0]);

                return 0;
        }
        return 0;
}

while( (rv = read(fd2[0], line, MAXLINE)) > 0)