我不明白为什么我的代码输出如下。它不遵循我在程序中编写的逻辑。我正在使用 System V 信号量 来同步线程。
这个程序应该只需要从标准输入到“主线程”的字符串,这些应该由子线程写入其“路径名”传递给 argv 的文件。为了简单起见,我删除了这部分,只留下了 scanf 和 printf,这完全被程序的逻辑搞砸了!
如何解决?
#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#define fflush(stdin) while(getchar()!='\n') //REMOVE THIS
void *gestore(void *);
char buf[10];
struct info
{
pthread_t tid[100];
int v[100];
};
struct info TID;
union semun
{
int val;
struct semid_ds *buf;
unsigned short *array;
struct seminfo *__buf;
};
int indice;
int id_sem;
void *gestore(void *str)
{
int fd, i, j;
struct sembuf op[1];
printf("Thread(%ld) CREATED\n",syscall(SYS_gettid));
fflush(stdout);
fd = open((char *)(str),O_CREAT|O_RDWR,0666);
if(fd==-1)
{
printf("Error\n");
return;
}
else
{
printf("File Opened\n");
fflush(stdout);
}
repeat:
op[0].sem_num=0;
op[0].sem_op=-1;
op[0].sem_op=0;
semop(id_sem,op,1);
printf("HELLO\n");
fflush(stdout);
for(i=0; i<5; i++)
{
if(write(fd,&(buf[2*i]),1)==-1)
{
printf("ErroreWrite\n");
fflush(stdout);
return;
}
else
{
printf("WRITED\n");
fflush(stdout);
}
}
op[0].sem_num=1;
op[0].sem_op=1;
op[0].sem_op=0;
semop(id_sem,op,1);
goto repeat;
if(close(fd)==-1)
{
printf("Errore close\n");
return;
}
else
{
printf("File CLOSED\n");
fflush(stdout);
}
}
int main(int argc, char *argv[])
{
if(argc<2)
{
printf("There must be at least 2 parameters\n");
fflush(stdout);
return -1;
}
int i;
indice = argc;
printf("Number of arguments:%d \n",argc);
fflush(stdout);
//SEM SYSTEM V
union semun arg;
struct sembuf op[1];
id_sem = semget(6534,2,IPC_CREAT|0666);
arg.val=0;
semctl(id_sem,0,SETVAL,arg);
arg.val=1;
semctl(id_sem,1,SETVAL,arg);
//////////////////////
for(i=0; i<(argc-1); i++)
{
pthread_create(&(TID.tid[i]),NULL,gestore,argv[i+1]);
}
while(1)
{
op[0].sem_num=1;
op[0].sem_op=-1;
op[0].sem_op=0;
semop(id_sem,op,1);
for(i=0;i<5;i++)
{
printf("Insert value(%d): \n",i);
fflush(stdout);
scanf("%c",&(buf[2*i]));
buf[2*i+1]='\0';
fflush(stdin);//USE while(getchar()!='\n');
}
op[0].sem_num=0;
op[0].sem_op=1;
op[0].sem_op=0;
semop(id_sem,op,1);
}
}
(a、b、c、d、e、f、g 是我从标准输入输入的)
这是我的输出:
Number of arguments:4
a
Thread(1048) CREATED
Thread(1049) CREATED
Thread(1050) CREATED
b
File OPENED
c
File OPENED
d
File OPENED
e
f
HELLO
g
HELLO
h
WRITED
i
WRITED
l
WRITED
m
WRITED
n
WRITED
o
WRITED
p
WRITED
q
WRITED
e
WRITED
r
WRITED
s
a
s
我的字符串“Insert Value(%d)...”在哪里?
将我定义的宏替换为fflus(stdin)如下写法:while(getchar()!='N');获得的输出是:
Number of arguments:4
Thread(1090) CREATED
Thread(1091) CREATED
Thread(1092) CREATED
File OPENED
File OPENED
HELLO
File OPENED
WRITED
HELLO
WRITED
WRITED
WRITED
WRITED
WRITED
WRITED
WRITED
WRITED
WRITED
在这种情况下,我没有发送任何输入字符就获得了这些输出。
最佳答案
揭开谜底。三胞胎:
- op[0].sem_num=0;
- op[0].sem_op=-1;
- op[0].sem_flg=0;
它到处写得很糟糕,如下所示:
- op[0].sem_num=0;
- op[0].sem_op=-1;
- op[0].sem_op=0; <------------
还与其他用户向我指出的错误定义相关联是一场灾难。
谢谢大家!
关于c - 使用信号量系统 V 的 Scanf 和 printf,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/56735804/