1 /* 
   2 cc test.c -o test 
   3 ./test
   4 */
   5 #include <stdio.h>
   6 #define SIZE 5
   7 #define FILENAME "test.txt"
   8 
   9 void clear(char *buffer)
  10 {
  11         for (int i = 0; i < SIZE; i++) {
  12                 *(buffer+i) = 0x00;
  13     }
  14 }
  15 
  16 int main(void)
  17 {
  18         printf("Hello World\n");
  19         FILE *f = fopen(FILENAME, "w");
  20         char buffer[SIZE];
  21         clear(buffer);
  22 
  23         for (int i = 0; i < 3; i++) {
  24             fwrite("aaaa\n", 1,SIZE, f);
  25         }
  26 
  27         fclose(f);
  28 
  29         FILE *r = fopen(FILENAME, "r");
  30         clear(buffer);
  31 
  32         int amount = -1;
  33 
  34         while (amount != 0 ) {
  35         amount = fread( buffer,1,SIZE,r );
  36         printf("%d\n",amount);
  37         if(amount !=0) {
  38             for(int k=0;k<amount;k++){
  39                       printf("%c", *(buffer+k) );
  40             }
  41             printf("\n");
  42             clear(buffer);
  43         }
  44         }
  45 
  46         fclose(r);
  47         return 0;
  48 }

   1 /* 
   2 cc pthread.c -o pthread -lpthread ./pthread 
   3 ./pthread
   4 */
   5 #include <stdio.h> 
   6 #include <stdlib.h> 
   7 #include <pthread.h>
   8 #include <string.h>
   9 #include <signal.h>
  10 #include <unistd.h>
  11 
  12 typedef struct data {
  13   char msg[128];
  14   int count;
  15 } threadData;
  16 
  17 
  18 void signalHandler(int signal){
  19   if(signal == SIGTERM){
  20     printf("Caught SIGTERM signal. Going to exit ...\n");
  21     exit(0);
  22   }
  23  
  24   if(signal == SIGUSR1){
  25     printf("USR1 caught \n");
  26   }
  27 
  28   if(signal == SIGUSR2){
  29     printf("USR2 caught \n");
  30   } 
  31 }
  32 
  33 void *threadCallback( void *ptr ) {
  34   char *message  = (char *) ((threadData *) ptr)->msg;
  35   int count =  ((threadData *) ptr)->count;
  36  
  37   while(count<10) {
  38     printf("%s count %d thread id %u \n", message,count , pthread_self() );
  39     sleep(1);
  40     count++;
  41   }
  42 }
  43 
  44 int main() {
  45   struct sigaction signalAction;
  46   memset (&signalAction, '\0', sizeof(signalAction));
  47   signalAction.sa_handler = &signalHandler;
  48 
  49   pthread_t thread1Id;
  50   int thread1Ret;
  51   threadData thread1Data;
  52   strcpy(thread1Data.msg,"Message 1234");
  53   thread1Data.count=5;
  54    
  55   pthread_t thread2Id;
  56   int thread2Ret;
  57   threadData thread2Data;
  58   strcpy(thread2Data.msg,"Message 54321");
  59   thread2Data.count=3;
  60   
  61   printf("Main thread id %u \n" , pthread_self() );
  62 
  63   thread1Ret = pthread_create( &thread1Id, NULL, threadCallback, (void*) &thread1Data);
  64   thread2Ret = pthread_create( &thread2Id, NULL, threadCallback, (void*) &thread2Data);
  65 
  66   if(thread1Ret || thread2Ret) {
  67     fprintf(stderr,"Error creating threads ");
  68     exit(EXIT_FAILURE);
  69   }
  70 
  71   // callback to signalHandler function
  72   sigaction(SIGTERM  , &signalAction, NULL);
  73   sigaction(SIGUSR1  , &signalAction, NULL);
  74   sigaction(SIGUSR2  , &signalAction, NULL);
  75 
  76   pthread_join( thread1Id, NULL);
  77   pthread_join( thread2Id, NULL);
  78   printf("Normal exit\n");
  79   exit(EXIT_SUCCESS);
  80 }