pid of a process in c with code examples

Introduction:

In computer science, a process can be defined as an instance of a computer program that is being executed. A process can also be thought of as a container for all the necessary resources that the program uses like memory space, input/output devices, processor time, etc. A Process ID (PID) is basically a numerical identifier that is assigned to each running process by the operating system. This PID can be used to uniquely identify a particular process and perform various operations on it like stopping the process, changing its priority, and many more.

In this article, we will discuss the PID of a process in C programming language. We will also provide some code examples to demonstrate how to obtain the PID of a process using different system calls.

Getting PID of the Current Process:

The first thing we need to know is how to obtain the PID of the current process i.e. the process in which the code is currently executing. This can be done using the getpid() system call. Here's an example:

#include <stdio.h>
#include <unistd.h>
int main()
{
    printf("The PID of the current process is: %d
", getpid());
    return 0;
}

This code will print the PID of the current process using the getpid() system call. The getpid() function returns an integer value that corresponds to the PID of the current process.

Getting PID of a Parent Process:

Sometimes, we might also need to obtain the PID of the parent process that created this process. We can use the getppid() system call to achieve this. Here's an example:

#include <stdio.h>
#include <unistd.h>
int main()
{
    printf("The PID of the parent process is: %d
", getppid());
    return 0;
}

This code will print the PID of the parent process using the getppid() system call. The getppid() function returns an integer value that corresponds to the PID of the parent process.

Getting PID of a Child Process:

In case we create a new process using the fork() system call, we might need to obtain the PID of the newly created child process. The fork() system call creates a copy of the current process and returns the PID of the child process in the parent process. Here's an example:

#include <stdio.h>
#include <unistd.h>
int main()
{
    int pid = fork();
    if(pid == 0)
    {
        printf("This is the child process, PID: %d
", getpid());
    }
    else if(pid > 0)
    {
        printf("This is the parent process, PID: %d
", getpid());
        printf("Child process PID: %d
", pid);
    }
    else
    {
        printf("Error creating child process!
");
    }
    return 0;
}

This code demonstrates how to obtain the PID of a newly created child process using the fork() system call. The fork() function returns the PID of the child process in the parent process and 0 in the child process.

Conclusion:

Process ID (PID) is a unique identifier assigned by the operating system to each running process. In this article, we have discussed how to obtain the PID of a process using various system calls in the C programming language. We have provided code examples to demonstrate how to get the PID of the current process, parent process, and child process using the getpid(), getppid(), and fork() system calls respectively. Understanding the PID of a process is crucial in performing different operations on processes, like stopping, restarting, prioritizing, and many more. With this article, we hope you have gained a deeper understanding of the PID of a process in C programming language.

let's dive deeper into the different topics discussed in the article.

Getting PID of the Current Process:

The getpid() system call is used to obtain the process ID (PID) of the current running process. It is a simple system call that returns the PID of the calling process. This number is unique for each running process and is assigned by the operating system. The pid_t data type is used to store the return value of the getpid() system call.

Here's a code example that demonstrates how to obtain the PID of the current process using the getpid() system call:

#include <stdio.h>
#include <unistd.h>

int main() {
  pid_t pid = getpid();
  printf("The current process ID is: %d
", pid);
  return 0;
}

Getting PID of a Parent Process:

The getppid() system call is used to obtain the PID of the parent process. It returns the PID of the parent process in which the current process was created. The pid_t data type is used to store the return value of the getppid() system call.

Here's a code example that demonstrates how to obtain the PID of the parent process using the getppid() system call:

#include <stdio.h>
#include <unistd.h>

int main() {
  pid_t ppid = getppid();
  printf("The parent process ID is: %d
", ppid);
  return 0;
}

Getting PID of a Child Process:

The fork() system call is used to create a new child process from the parent process. When a child process is created, the fork() system call returns the PID of the child process to the parent process, and it returns 0 to the child process. This allows the parent process to obtain the PID of the newly created child process. The pid_t data type is used to store the return value of the fork() system call.

Here's a code example that demonstrates how to obtain the PID of a newly created child process using the fork() system call:

#include <stdio.h>
#include <unistd.h>

int main() {
  pid_t pid = fork();
  
  if (pid == 0) {
    // This is the child process.
    printf("This is the child process, PID: %d
", getpid());
  } else if (pid > 0) {
    // This is the parent process.
    printf("This is the parent process, PID: %d
", getpid());
    printf("Child process PID: %d
", pid);
  } else {
    // There was an error. 
    printf("Error creating child process.
");
  }
  
  return 0;
}

Conclusion:

In conclusion, obtaining the PID of a process is a crucial part of any operating system. It allows users to identify and manipulate processes running on a system. In this article, we discussed various techniques to obtain the PID of the current process, the parent process, and child processes. The getpid(), getppid(), and fork() system calls are commonly used to obtain the PID of a process in the C programming language. Being able to obtain the PID of a process is a critical skill for any programmer working with operating system-level tasks.

Popular questions

1. What system call is used to obtain the PID of the current process in C programming language?
   Answer: The getpid() system call is used to obtain the PID of the current process in C programming language.

2. What data type is used to store the return value of the getpid() and getppid() system calls?
   Answer: The pid_t data type is used to store the return value of the getpid() and getppid() system calls.

3. What system call is used to create a new child process from the parent process in C programming language?
   Answer: The fork() system call is used to create a new child process from the parent process in C programming language.

4. What does the fork() system call return to the parent process and child process?
   Answer: The fork() system call returns the PID of the child process to the parent process, and it returns 0 to the child process.

5. Why is obtaining the PID of a process important in operating systems?
   Answer: Obtaining the PID of a process is important in operating systems because it allows users to identify and manipulate processes running on a system. It is a crucial part of many operating system tasks like stopping, restarting, prioritizing, and many more.

Tag

"ProcessID"