Question

C LANGUAGE PROGRAM:

You have the program that creates a parent and child. They communicate via the pipe.

The parent writes into the pipe and child reads the data from the pipe.

All you got to is replace FILL_IN_THE_BLANK with appropriate values or function names

and just type the values of each TASKS, I don't need the c program.

TASK_1 =

TASK_2 =

TASK_3 =

TASK_4 =

4 of them [ 5 points each ]

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When you run the program after filling the value, It should print

Reading in child process: Hello World from Parent

I am done waiting

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Then, I want a report of what the program is doing , line by line. [ 10 points ]

Your responses should be :

Why am I closing some pipe descriptors?

What am I writing ?

What am I writing to where ?

What am I reading?

Where am I reading from.

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THE FILE CONTENTS:

#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#define TASK_1 FILL_IN_THE_BLANK
#define TASK_2 FILL_IN_THE_BLANK
#define TASK_3 FILL_IN_THE_BLANK
#define TASK_4 FILL_IN_THE_BLANK

#define MAX_LINE 32

int
main(int argc, char *argv[])
{
char *strConstant = "Hello World from Parent";

int pipefd [ TASK_1 ]; // TASK 1: FILL IN THE BLANK
pid_t cpid;
char buf[ MAX_LINE ];

if ( TASK_2 ( pipefd ) == -1) { // TASK2 : FILL IN THE BLANK TO CREATE
// PIPE
perror("pipe");
exit(EXIT_FAILURE);
}

cpid = TASK_3 (); // TASK 3: WHO DO I FORK ?
if (cpid == -1) {
perror("fork");
exit(EXIT_FAILURE);
}

if (cpid == TASK_4 ) { /* TASK 4: Check for child process */
close(pipefd[1]); /* Close unused write end */

int num ;
num = read( pipefd[0] , &buf, MAX_LINE) ;
printf ( " Reading in child process: ");
printf( "%s \n", buf );

close( pipefd [0] ); //
sleep ( 1 );
exit ( 0 ) ;

} else { /* Parent writes argv[1] to pipe */
close( pipefd[0] ); /* Close unused read end */
write( pipefd[1], strConstant, strlen ( strConstant) );
close( pipefd[1] ); /* Reader will see EOF */
wait(NULL); /* Wait for child */
printf ( "I am done waiting \n");
}

exit( EXIT_SUCCESS);
}

Answer 1

1.Why am I closing some pipe descriptors?

We have to close the original pipe file descriptor of the pipe.We should close file descriptors that we don't need, and that's what this program does. This is to avoid the duplicate pipes

2.What am I writing ?
"Hello World from Parent"

3.What am I writing to where ?
//parent writes to the pipe.The string constant written is "Hello World from Parent"
The program statements follows--
write( pipefd[1], strConstant, strlen ( strConstant) );

What am I reading?
Hello World from Parent

Where am I reading from.
//child get the data from pipe and stored in buf

num = read( pipefd[0] , &buf, MAX_LINE) ;
printf ( " Reading in child process: ");

THE FILE CONTENTS:
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#define TASK_1 1
#define TASK_2 pipe
#define TASK_3 pipe( pipefd )
#define TASK_4 fork ( )
#define MAX_LINE 32
int
main(int argc, char *argv[])
{
char *strConstant = "Hello World from Parent";
int pipefd [ TASK_1 ];
pid_t cpid;
char buf[ MAX_LINE ];
if ( TASK_2 ( pipefd ) == -1) {
perror("pipe");
exit(EXIT_FAILURE);
}
cpid = TASK_3 ();
if (cpid == -1) {
perror("fork");
exit(EXIT_FAILURE);
}
if (cpid == TASK_4 ) { /* TASK 4: Check for child process */
close(pipefd[1]); /* Close unused write end */
int num ;
num = read( pipefd[0] , &buf, MAX_LINE) ;
printf ( " Reading in child process: ");
printf( "%s \n", buf );
close( pipefd [0] ); //closing the pipe descriptor
exit ( 0 ) ;
} else { /* Parent writes argv[1] to pipe */
close( pipefd[0] ); /* Close unused read end */
write( pipefd[1], strConstant, strlen ( strConstant) );
close( pipefd[1] ); /* Reader will see EOF */
wait(NULL); /* Wait for child */
printf ( "I am done waiting \n");
}

exit( EXIT_SUCCESS);
}