stuff

Examples/pthreads/pthreads2.c

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+/*
+ * pthreads2.c - Shows how to create and wait for multple
+ *               threads (beyond the main thread)
+ *               Threads prints out its thread ID and process ID.
+ *               Shows that threads share the same process ID
+ *               but all have their own thread ID
+ */
+
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int global_value = 10;
+
+// thread_routine
+//   writes to a global variable - shows that
+//   global data is shared between threads
+//
+// NOTE: that parameters and return value are pointers
+void* thread_routine()
+{
+    for(int i = 0; i < 10; i++) {
+        printf("%lu %d: THREAD READS GLOBAL VALUE: %d\n", pthread_self(), getpid(), global_value);
+        global_value++;
+        sleep(1);
+    }
+    return NULL;
+}
+
+int main()
+{
+    // Create 5 threads
+    pthread_t thr_id[5];
+    for(int i = 0; i < 5; i++) {
+        if(pthread_create(&thr_id[i], NULL, thread_routine, NULL) == -1) {
+            printf("COULD NOT CREATE A THREAD\n");
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    // Wait for all threads to finish
+    for(int i = 0; i < 5; i++) {
+        pthread_join(thr_id[i], NULL);
+    }
+
+    // Print out final value of global data
+    printf("%lu %d PARENT READS GLOBAL: %d\n", pthread_self(), getpid(), global_value);
+
+    // Return success
+    return 0;
+}