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How to Create a Ring-Like Structure for Multi-Process Communication in C

In this comprehensive guide, we'll dive into a C program that demonstrates the art of passing values among multiple processes, creating an intricate ring-like structure. We provide you with both the code and an in-depth theoretical discussion of each code block, empowering you with a thorough understanding of the entire process. Whether you're a novice programmer looking to expand your knowledge or an experienced developer seeking to master inter-process communication, this guide has something valuable for everyone. Get ready to unravel the intricacies of multi-process communication in C and take your programming skills to the next level.

Building a Ring Structure for Efficient Communication in C

Explore creating a ring structure for multi-process communication in C on our website. This comprehensive guide delves into the intricacies of inter-process communication, providing you with a deep understanding of process synchronization and performance optimization. If you need help with your C assignment, whether it's related to multi-process communication or any other aspect of C programming, our expert team is here to assist you in achieving your academic and programming goals.

Block 1: Header Includes and Error Handling

```c #include #include #include #include #include #include ```

This block includes essential header files for the program and defines a function `critical_error` to handle errors. It also sets up function signatures for `create_child`, `usr_sig_handler`, and `main`.

Block 2: `critical_error` Function

```c void critical_error(char *msg) { perror(msg); exit(1); } ```

This function serves to print error messages and exit the program with an error status when errors occur.

Block 3: `create_child` Function

```c pid_t create_child(int N, int leader, int cnt) { pid_t pid; char args[4][10]; // Convert the arguments to strings for passing them to the child program sprintf(args[0], "./ring"); sprintf(args[1], "%d", N); sprintf(args[2], "%d", leader); sprintf(args[3], "%d", cnt); // Fork the process pid = fork(); if (pid == -1) critical_error("error in fork()"); else if (pid == 0) // We are in the child process { if (execl("./ring", args[0], args[1], args[2], args[3], (char *) NULL) < 0) critical_error("error in execl()"); } // Return the child PID return pid; } ```

This function is responsible for creating a new child process with the given parameters. It forks the current process and executes the program with the arguments passed. The child process is created to participate in the ring structure.

Block 4: Signal Handler

```c void usr_sig_handler(int sig) { // Nothing to do here } ```

This is a signal handler function. It doesn't perform any action but is set up to handle the SIGUSR1 signal.

Block 5: `main` Function

```c int main(int argc, char **argv) { int leader, N, cnt, i, is_leader; sigset_t mask; struct sigaction action; pid_t child; struct timespec start, stop; float elapsed_time; // If the number of arguments is incorrect, print usage if (argc != 4) { printf("Usage: %s N leader cnt\n", argv[0]); return 0; } // Convert the arguments to integers N = atoi(argv[1]); leader = atoi(argv[2]); cnt = atoi(argv[3]); // Set a flag to see if this process is the leader is_leader = (leader == 0); // Fill in sigaction to call our handler with SIGUSR1 action.sa_handler = usr_sig_handler; // Don't mask signals if (sigemptyset(&action.sa_mask)) critical_error("error in sigemptyset()"); action.sa_flags = 0; // Set our handler as the SIGUSR1 handler if (sigaction(SIGUSR1, &action, NULL) < 0) critical_error("error in sigaction()"); // Create an empty set of blocked signals if (sigemptyset(&mask) < 0) critical_error("error in sigemptyset()"); // If we are the leader, use the PID and calculate the time if (is_leader) { leader = getpid(); // Get the initial time if (clock_gettime(CLOCK_REALTIME, &start) < 0) critical_error("error in clock_gettime()"); } // If this is not the last process, create a new child if (N > 1) child = create_child(N - 1, leader, cnt); // Send signals in a ring for (i = 0; i < cnt; i++) { if (N == 1) { // Signal the leader if (kill(leader, SIGUSR1) < 0) critical_error("error in kill()"); } // Wait to receive the SIGUSR1 signal // sigsuspend always returns -1 (void) sigsuspend(&mask); if (N > 1) { // Signal the child if (kill(child, SIGUSR1) < 0) critical_error("error in kill()"); } } // If we are the leader, calculate the elapsed time and print the results if (is_leader) { // Get the final time if (clock_gettime(CLOCK_REALTIME, &stop) < 0) critical_error("error in clock_gettime()"); // Calculate elapsed time elapsed_time = (stop.tv_sec - start.tv_sec) + (stop.tv_nsec - start.tv_nsec) / 1e9; // Print result printf("%d %7.3e\n", cnt, elapsed_time); } return 0; } } ```

The `main` function is the entry point of the program. It handles command-line arguments, sets up signal handling, creates child processes, sends signals in a ring, and calculates and prints elapsed time for the leader process.

Block 6: Command-Line Argument Processing

This section of the `main` function processes the command-line arguments and converts them into integers.

Block 7: Setting Up Signal Handling

This section sets up the signal handler for SIGUSR1. It uses the `sigaction` function to specify the `usr_sig_handler` function to handle this signal.

Block 8: Creating an Empty Set of Blocked Signals

Here, an empty set of blocked signals is created to be used with `sigsuspend`.

Block 9: Leader Process Time Measurement

If the current process is the leader, it calculates the initial time using `clock_gettime` to measure the time elapsed during the execution of the program.

Block 10: Creating Child Processes

If N is greater than 1, this block creates a child process by calling the `create_child` function.

Block 11: Sending Signals in a Ring

This section is responsible for sending signals around the ring. It sends signals from the leader to its child and, if N is greater than 1, from the child to its child, creating a ring structure. It uses `kill` to send signals and `sigsuspend` to wait for signals.

Block 12: Leader Process Time Calculation and Printing

If the current process is the leader, it calculates the elapsed time using `clock_gettime`, and then it prints the count of signals and the elapsed time.

Shell Script

The provided shell script is a separate script that runs the C program with different values of `cnt` and records the results in an output file.


In conclusion, this C program creates a ring of processes, passes signals in a ring structure, and measures the time taken by the leader to complete the signal passing. The shell script runs this program with different signal counts and records the results. This practical exercise not only demonstrates inter-process communication but also provides insights into measuring and optimizing process interaction in multi-processing environments. As you explore the code and experiment with various signal counts, you'll gain a deeper understanding of process synchronization and performance tuning, essential skills for building robust and efficient multi-process applications. So, take these insights with you and apply them to your future programming endeavors, where efficient process communication is vital for success.