Compile the two files and run the files in two SSH terminals respectively. Add a piece of code to each file so that (1) each process shows its pid using printf and (2) then sends its pid to another side using the named pipe. Hint: use getpid() in previous labs. What is your modified source code for namedpipe_p1.c only?
Named pipe is for a bidirection communication.
A named pipe (also known as a FIFO) is one of the methods for inter-process communication. Usually a named pipe appears as a file and generally processes attach to it for inter-process communication. A FIFO file is a special kind of file on the local storage which allows two or more processes to communicate with each other by reading/writing to/from this file. A FIFO special file is entered into the file system by calling mkfifo() in C. Once we have created a FIFO special file in this way, any process can open it for reading or writing, in the same way as an ordinary file.
The following code is for the code file namedpipe_p1.c.
// This process writes first, then reads
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
int main()
{
int fd;
// FIFO file path
char * myfifo = "./myfifo";
// Creating the named file(FIFO)
// mkfifo(<pathname>, <permission>)
mkfifo(myfifo, 0666);
char arr1[80], arr2[80];
// Open FIFO for write only
fd = open(myfifo, O_WRONLY);
// Take an input arr2ing from user.
// 80 is maximum length
printf("your message: ");
fgets(arr2, 80, stdin);
// Write the input arr2ing on FIFO
// and close it
write(fd, arr2, strlen(arr2)+1);
close(fd);
// Open FIFO for Read only
fd = open(myfifo, O_RDONLY);
// Read from FIFO
read(fd, arr1, sizeof(arr1));
// Print the read message
printf("Received: %s\n", arr1);
close(fd);
return 0;
}
The following code is for another code file namedpipe_p2.c.
// This program reads first, then writes
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
int main()
{
int fd1;
// FIFO file path
char * myfifo = "./myfifo";
// Creating the named file(FIFO)
// mkfifo(<pathname>,<permission>)
mkfifo(myfifo, 0666);
char str1[80], str2[80];
// First open in read only and read
fd1 = open(myfifo,O_RDONLY);
read(fd1, str1, 80);
// Print the read string and close
printf("Received: %s\n", str1);
close(fd1);
// Now open in write mode and write
// string taken from user.
fd1 = open(myfifo,O_WRONLY);
printf("your message: ");
fgets(str2, 80, stdin);
write(fd1, str2, strlen(str2)+1);
close(fd1);
return 0;
}
Compile the two files and run the files in two SSH terminals respectively.
Add a piece of code to each file so that (1) each process shows its pid using printf and (2) then sends its pid to another side using the named pipe. Hint: use getpid() in previous labs.
What is your modified source code for namedpipe_p1.c only?
What are the results of the two SSH terminals? Please paste the screenshots?
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