The presentation aims towards imparting the concept of PIPES and the mechanism they follow. REFERENCES : Operating System 8th Edition by : Abraham Silberschatz

1. PIPES
A pipe in computing is way of communication between more than one process
.Pipe strictly follows the Inter Process Communication.
Pipes were the one of the first mechanism in early UNIX systems.It provides one
of the simplest way of communication between different process

2. General View of Pipe

3. Types of Pipes
• Ordinary Pipes
• Named Pipes
Ordinary Pipes:
The Ordinary pipe in Operating Systems allows the two procedures to communicate in a standard
way: the procedure writes on the one end (the write end) and reads on the consumer side or another
end (the read-end). As a result, ordinary pipes are unidirectional, allowing only one-way
communication as shown in a figure.

4. Ordinary Pipe

5. Ordinary Pipes in Unix System
#define BUFFER_SIZE 25
#define READ_END 0 // fd[0] is the read-end of the pipe
#define WRITE_END 1 //fd[1] is the write-end
int main(void)
{
char write_msg[BUFFER_SIZE]
char read_msg[BUFFER_SIZE];
int fd[2];
pid_t pid;

6. Example Continued
• I* create the pipe *I
• if (pipe(fd) == -1) {
• fprintf(stderr,"Pipe failed");
• return 1;
• }
• I* fork a child process *I
• pid = fork();

7. • if (pid < 0) { I* error occurred *I
• fprintf(stderr, "Fork Failed");
• return 1;
• }
• if (pid > 0) { I* parent process *I
• }
• I* close the unused end of the pipe *I
• close(fd[READ_END]);

8. • I* write to the pipe *I
• write(fd[WRITE_END], write_msg, strlen(write_msg)+1);
• I* close the write end of the pipe *I
• close(fd[WRITE_END]);
• else { I* child process *I
• }

9. Example Continued
• I* close the unused end of the pipe *I
• close(fd[WRITE_END]);
• I* read from the pipe *I
• read(fd[READ_END], read_msg, BUFFER_SIZE);
• printf ("read %s", read_msg) ;
• I* close the write end of the pipe *I
• close(fd[READ_END]); }
• return 0; }

10. In Windows
•
Ordinary pipes on Windows systems are termed anonymous pipes.
• the pipe is created by using CreatePipe() function
• Functionality, they are unidirectional.
• Readfile() and Writefile() functions are used for reading and writing to the file.
Point of significance:
Note that ordinary pipes require a parent-child relationship between computing processes in both UNIX and Windows
systems. This means that pipes can be used only for communication between processes on the same machine.

11. Named pipes

12. • Communication can be bi-directional
• no parent-child relationship is required between process
• More than two process can communicate with each other a time
• named pipes exist after completion and termination of all the processes

13. In Unix
Name pipes referred to as FIFO (first in first out) in UNIX systems.
Once they created.
They appear as typical files in the file systems.
A FIFO is created with the mkfifo() system call and manipulated with open(), read(), write() and close() system
calls.
FIFO supports two-way communication, only half-duplex transmission is permitted.

14. In Windows
• Much richer communication mechanism between processes rather than UNIX systems
• Full-duplex communication is allowed in Windows named pipe
• The communication may run from either different sides or from the same side of the pipe at a same time
• Name pipe is created with CreateNamedPipe() function, and a client can connect the named pipe using
ConnectNamedPipe(). Communication over the named pipe can be accomplished using the ReadFile() and
WriteFile() functions
POINT OF SIGNIFICANCE:
Windows provides the facility of the communication between processed residing on different machines.