pthread_cancel() in C with example

prerequisite: Multithreading, pthread_self() in C with Example

pthread_cancel() = This function cancel a particular thread using thread id. This function send a cancellation request to the thread.

Syntax : – int pthread_cancel(pthread_t thread);

First Program : – Cancel self thread

// C program to demonstrates cancellation of self thread
// using thread id
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

void* calls(void* ptr)
{
    printf("GeeksForGeeks");

    // To exit the current thread
    // pthread_self() return the particular thread id
    pthread_cancel(pthread_self());

    return NULL;
}

int main()
{
    // NULL when no attribute
    pthread_t thread;

    // calls is a function name
    pthread_create(&thread, NULL, calls, NULL);

    // Waiting for when thread is completed
    pthread_join(thread, NULL);

    return 0;
}

Output:

GeeksForGeeks

If you use Linux then compile this program gcc program_name.c -lpthread

Second Program : – Cancel other thread

// C program to demonstrates cancellation of another thread
// using thread id
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>

// To Count
int counter = 0;

// for temporary thread which will be
// store thread id of second thread
pthread_t tmp_thread;

// thread_one call func
void* func(void* p)
{
    while (1) {

        printf("thread number one\n");
        sleep(1);   // sleep 1 second
        counter++;

        // for exiting if counter = = 5
        if (counter = = 2) {

            // for cancel thread_two
            pthread_cancel(tmp_thread);

            // for exit from thread_one
            pthread_exit(NULL);
        }
    }
}

// thread_two call func2
void* func2(void* p)
{

    // store thread_two id to tmp_thread
    tmp_thread = pthread_self();

    while (1) {
        printf("thread Number two");
        sleep(1); // sleep 1 second
    }
}

// Driver code
int main()
{

    // declare two thread
    pthread_t thread_one, thread_two;

    // create thread_one
    pthread_create(&thread_one, NULL, func, NULL);

    // create thread_two
    pthread_create(&thread_two, NULL, func2, NULL);

    // waiting for when thread_one is completed
    pthread_join(thread_one, NULL);

    // waiting for when thread_two is completed
    pthread_join(thread_two, NULL);

}

Output:

thread number one
thread number two
thread number one 
thread number two

If you use Linux then compile this program gcc program_name.c -lpthread