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The program will then create a separate thread that outputs all the prime numbers less than or equal to the number entered by the user.

1#include <pthread.h>

  2#include <stdio.h>

  3#include <stdlib.h>

  4

  5 void*runner(void *param); /* the thread */

  6

  7 intmain(int argc, char *argv[]) {

  8

  9       //arg값이 2인지확인

10       if(argc < 2) {

11                 fprintf(stderr, "사용법:./pthreads.out <정수값>\\n");

12                       exit(1);

13                          }

14

15          // 입력값이 2이상인값인지 검증

16          if(atoi(argv[1]) < 2) {

17                    fprintf(stderr, "사용법:%d 무조건  >= 2\\n",atoi(argv[1]));

18                          exit(1);

19                             }

20

21             pthread_t tid;       //쓰레드 ID선언

22                pthread_attr_t attr; //쓰레드의 속성 설정

23

24                   printf("소수(PrimeNumber)값들 : ");

25

26                      //쓰레드의 속성값 초기화

27                      pthread_attr_init(&attr);

28                         //쓰레드를 생성함

29                         pthread_create(&tid,&attr,runner,argv[1]);

30                            //쓰레드가 끝날때 까지 기다림

31                            pthread_join(tid,NULL);

32                               printf("\\n완료\\n");

33 }

34

35//runner함수를 통해 쓰레드가 실행됨

36 void*runner(void *param) {

37       int i,j,upper = atoi(param);

38          /* 소수가 맞는지 체크함 */

39          for(i = 2; i < upper; i++) {

40                 int trap = 0;

41                       /* 각각의 숫자가 나누어 지는지체크 */

42                       for(j = 2; j < i; j++) {

43                                    int result = i % j;

44                                             /* 어떤수가 소수로나누어 지면 소수가 아니므로 무시.*/

45                                             if(result == 0) {

46                                                             trap = 1;

47                                                                        break;

48                                                                                 }

49                                                   }

50                             //자기 자신으로만 나누어 지면그것은 소수이다.

51                             if(trap == 0) {

52                                          printf("[%d] ", i);

53                                                }

54                                }

55             //쓰레드 종료

56             pthread_exit(0);

57 }

~