Write an IPC program using pipe using C++ and Python

Q: Process A accepts a character string and Process B inverses the string. Pipe is used to establish communication between A and B processes using C++ & Python


Note: The process communication in this example takes place through name pipes. Unnamed in c++ simpler and can be found on Internet. Or better still just type info pipe on terminal you will get the entire code.

Code

Reader.cpp

#include <fcntl.h>
#include <iostream>
#include <sys/stat.h>
#include <unistd.h>
#include <string>
#include <string.h>

#define MAX_BUF 1024
using namespace std;

char* strrev(char *str){
    int i = strlen(str)-1,j=0;

    char ch;
    while(i>j)
    {
        ch = str[i];
        str[i]= str[j];
        str[j] = ch;
        i--;
        j++;
    }
    return str;

}


int main()
{
    int fd;
    char *myfifo = "/tmp/fifopipe";
    char buf[MAX_BUF];

    /* open, read, and display the message from the FIFO */
    fd = open(myfifo, O_RDONLY);
    read(fd, buf, MAX_BUF);
    cout<<"Received:"<< buf<<endl;
    cout<<"The reversed string is \n"<<strrev(buf)<<endl;
    close(fd);
    return 0;
}

Writer.cpp

#include <fcntl.h>
#include <iostream>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <string>
#include <string.h>
using namespace std;
int main()
{
    int fd;
    char * myfifo = "/tmp/fifopipe";

    /* create the FIFO (named pipe) */
    mkfifo(myfifo, 0666);

    /* write message to the FIFO */
    fd = open(myfifo, O_WRONLY);
    char *msg;
    msg="This is the string to be reversed";
    write(fd, msg, strlen(msg)+1);
    close(fd);

    /* remove the FIFO */
    unlink(myfifo);

    return 0;
}

Output

On two seperate terminal tabs

First

[te@dbsl2 3101]$ ./writer
[te@dbsl2 3101]$

Second

[te@dbsl2 3101]$ ./reader
Received:This is the string to be reversed
The reversed string is
desrever eb ot gnirts eht si sihT
[te@dbsl2 3101]$

Python

In python we can use ipc using fifo as follows

Writer

import os
path= "/home/hulk/myProgram.fifo"
os.mkfifo(path)
fifo=open(path,'w')
string=raw_input("Enter String to be reversed:\t ")
fifo.write(string)
fifo.close()

Reader

import os
import sys

path= "/home/hulk/myProgram.fifo"

fifo=open(path,'r')
str=fifo.read()
revstr=str[::-1]
print "The Reversed String is",revstr
fifo.close()

Output

Writer

hulk@unknown:~$ python writer.py
Enter the string: reverseme

Reader

hulk@unknown:~$ python reader.py
Reversed String is emesrever

Unnamed pipe

import os,sys
 
fdr,fdw=os.pipe(); 
procid=os.fork();
  
if pid:   #this is the parent process section it will read
 os.close(fdw)
 print "reversed string is ", os.fdopen(fdr).read()[::-1]
 sys.exit(0)

else:   #this is the child process section it will write 
 os.close(fdr)
 os.fdopen(fdw,'w').write(raw_input("Enter String: "))
 sys.exit(0)

Output

hulk@unknown:~$ python pipe.py
Enter String: reversemereversed string is  emesrever