As developers, we are constantly looking for ways to optimize our code and make our programs run more efficiently. One aspect of this is managing the priority of processes within our system. In this article, we will dive into the world of process priority manipulation in the C programming language, specifically focusing on how to change the priority of the current process.
Before we get into the details, let's first understand what process priority is and why it is important. Process priority is a way to determine the level of importance of a process within the system. A higher priority process will be given more resources and will be executed before a lower priority process. This is crucial in ensuring that critical processes are given priority and run smoothly, while non-essential processes do not hinder the system's performance.
In C, process priority is managed through the use of the "nice" system call. This call allows us to change the priority of a process by specifying a value between -20 to +19, with -20 being the highest priority and +19 being the lowest. The default priority of a process is 0.
To change the priority of the current process, we first need to obtain its process ID (PID). This can be done using the "getpid()" function. Once we have the PID, we can call the "nice()" system call and pass in the desired priority value.
Let's consider an example where we want to increase the priority of our current process by 5. We would use the following code:
#include <stdio.h>
#include <unistd.h>
int main() {
//get current process ID
pid_t pid = getpid();
//increase priority by 5
int new_priority = nice(5);
//check if priority was successfully changed
if(new_priority == -1){
printf("Unable to change process priority");
} else {
printf("Process with PID %d now has a priority of %d", pid, new_priority);
}
return 0;
}
In the above code, we first obtain the PID of our current process using the "getpid()" function. Then, we call the "nice()" system call with a value of 5 and store the return value in a variable called "new_priority". We then check if the priority was successfully changed and print out the new priority value along with the process ID.
It is important to note that the "nice()" system call can only decrease the priority of a process by a maximum of 19. If we try to increase the priority by more than 19, the call will fail and return -1.
Now, let's consider a scenario where we want to decrease the priority of our current process. We can do this by passing in a negative value to the "nice()" system call. Let's say we want to decrease the priority by 10. We would use the following code:
#include <stdio.h>
#include <unistd.h>
int main() {
//get current process ID
pid_t pid = getpid();
//decrease priority by 10
int new_priority = nice(-10);
//check if priority was successfully changed
if(new_priority == -1){
printf("Unable to change process priority");
} else {
printf("Process with PID %d now has a priority of %d", pid, new_priority);
}
return 0;
}
In this case, we pass in a value of -10 to the "nice()" system call and store the return value in "new_priority". Again, we check if the priority was successfully changed and print out the new priority value along with the process ID.
It is worth mentioning that the "nice()" system call is not available on all operating systems. In such cases, we can use the "setpriority()" function, which has a similar functionality.
In conclusion, managing process priority is an important aspect of optimizing the performance of our programs. In this article, we have seen how to change the priority of the current process in C using the "nice()" system call. By understanding and utilizing process priority manipulation, we can ensure that our programs run smoothly and efficiently. Happy coding!
