semaphore.c

这个资料非常不错

/**************
 * semaphore.c*
 **************/

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
//#include <semaphore.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>

#define PERMS S_IRUSR|S_IWUSR
#define MAX_CANON 100
void init_semaphore_struct(struct sembuf *sem,
		int semnum,int semop,int semflg)
{
sem->sem_num=semnum;
sem->sem_op=semop;
sem->sem_flg=semflg;
}

int del_semaphore(int semid)
{
#if 1
return semctl(semid,0,IPC_RMID);
#endif
}

int main(int argc,char **argv)
{
 char buffer[MAX_CANON],*c;
 int i,n;
 int semid,semop_ret,status;
 pid_t childpid;
 struct sembuf semwait,semsignal;

 if((argc!=2)||((n=atoi(argv[1]))<1))
  {
  fprintf(stderr,"Usage:%s number\n\a",argv[0]);
  exit(1);
  }
 
 if((semid=semget(IPC_PRIVATE,1,PERMS))==-1)
   {
  fprintf(stderr,"[%d]:Acess Semaphore Error:%s\n\a",
  getpid(),strerror(errno));
  exit(1);
   }

init_semaphore_struct(&semwait,0,-1,0);

init_semaphore_struct(&semsignal,0,1,0);

if(semop(semid,&semsignal,1)==-1)
 {
fprintf(stderr,"[%d]:Increment Semaphore Error:%s\n\a",
getpid(),strerror(errno));
if(del_semaphore(semid)==-1)
        fprintf(stderr,"[%d]:Destroy Semaphore Error:%s\n\a",
                getpid(),strerror(errno));
exit(1);
 }
for(i=0;i<atoi(argv[1]);i++)
 if(childpid=fork()) break;

sprintf(buffer,"[i=%d]-->[Process=%d]-->[Parent=%d]-->[Child=%d]\n",
i,getpid(),getppid(),childpid);
c=buffer;

while(((semop_ret=semop(semid,&semwait,1))==-1)&&(errno==EINTR));
if(semop_ret==-1)
 {
fprintf(stderr,"[%d]:Decrement Semaphore Error:%s\n\a",
   getpid(),strerror(errno));
 }
else
 {
while(*c!='\0')fputc(*c++,stderr);
while(((semop_ret=semop(semid,&semsignal,1))==-1)&&(errno==EINTR));
if(semop_ret==-1)
         fprintf(stderr,"[%d]:Increment Semaphore Error:%s\n\a",
                        getpid(),strerror(errno));
 }

while((wait(&status)==-1)&&(errno==EINTR));
if(i==1)
 if(del_semaphore(semid)==-1)
        fprintf(stderr,"[%d]:Destroy Semaphore Error:%s\n\a",
                        getpid(),strerror(errno));
exit(0);
}