How to Run Two Child Processes Sequentially in C

Описание: Learn how to execute two child processes in `C` sequentially using `fork()`, `execvp()`, and `waitpid()`. This guide provides clear examples and explanations of managing child processes in your C programs.
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How to Run Two Child Processes Sequentially in C

When developing applications in C, you may encounter the need to execute multiple child processes. While many examples focus on executing these processes in parallel, sometimes you need to run them sequentially. In this guide, we will explore how to create two child processes using fork() and ensure that one runs after the other, using wait() to synchronize their execution.

Understanding the Problem

You want to achieve the following in your program:

Fork two child processes.

Execute one predetermined executable in the first child.

Wait for the first child process to complete.

Execute a second predetermined executable in the second child after the first has finished.

Return control back to the parent process once both child processes have executed.

This can be efficiently managed with the use of fork(), execvp(), and waitpid() functions available in the C programming language.

Breaking Down the Solution

To accomplish the task, let's break it down step by step. Below are the essential functions you will need:

1. Forking a Child Process

The fork() function is used to create a new process by duplicating the calling process. Here's how to implement it with error handling:

[[See Video to Reveal this Text or Code Snippet]]

2. Executing a Command with execvp()

After forking, you can replace the child process's memory space with a new program image using execvp(). This function takes the command you want to run and its arguments:

[[See Video to Reveal this Text or Code Snippet]]

3. Waiting for the Child to Complete

To ensure that the child process has finished executing before proceeding, use waitpid():

[[See Video to Reveal this Text or Code Snippet]]

Complete Example Code

Now that we understand each component, let's look at some complete code snippets to run two commands sequentially. Here’s how you can implement this in a C program:

[[See Video to Reveal this Text or Code Snippet]]

Final Notes

This example effectively demonstrates how to fork two child processes and ensure they execute in sequence. Remember:

Error Handling: It's important to check for errors at each stage to avoid unexpected behaviors in your program.

Avoiding Shell: Using execvp() instead of invoking a shell avoids issues concerning path handling and command execution.

With this approach, you can ensure smooth execution of multiple processes in your C application. Happy coding!