多线程 linux下gcc编译一直通不过

Question

#include
2 #include
3 #include
4 #include
5
6 void print(pid_t);
7
8 sem_t *sem;
9 int val;
10 int main(int argc,char *argv[])
11 {
12 int n = 0;
13 if(argc != 2);
14 {
15 printf("please input afile name!\n");
16 exit(1);
17 }
18 sem = sem_open(argv[1],O_CREAT,0644,2);
19
20 while(n++<5)
21 {
22 if(fork()==0)
23 {
24 sem_wait(sem);
25 print(getpid());
26 sleep(1);
27 sem_post(sem);
28 printf("I'm finished,my pid is %d\n",getpid());
29 return 0;
30 }
31 }
32
33 wait();
34 sem_close(sem);
35 sem_unlink(argv[1]);
36 exit(0);
37 }
38
39 void print(pid_t pid)
40 {
41 printf("I get it,my pid is %d\n",pid);
42 sem_getvalue(sem,&val);
43 printf("Now the value have %d\n",val);
44 }

Answer 1

try compile this with

gcc sem.c -o sem -lrt

 #include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <semaphore.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

void print(pid_t);

sem_t *sem;
int val;
 int main(int argc,char *argv[])
 {
 int n = 0;
 if(argc != 2);
 {
 printf("please input afile name!\n");
 exit(1);
 }
 sem = sem_open(argv[1],O_CREAT,0644,2);

 while(n++<5)
 {
 if(fork()==0)
 {
 sem_wait(sem);
 print(getpid());
 sleep(1);
 sem_post(sem);
 printf("I'm finished,my pid is %d\n",getpid());
 return 0;
 }
 }

 wait();
 sem_close(sem);
 sem_unlink(argv[1]);
 exit(0);
 }

 void print(pid_t pid)
 {
 printf("I get it,my pid is %d\n",pid);
 sem_getvalue(sem,&val);
 printf("Now the value have %d\n",val);
 }