如何同时正确使用管道和信号? [英] How to use pipes and signals correctly at the same time?
问题描述
我有2个孩子,我想从孩子们向父母发送信号,并给出一个从父母到每个孩子的答案(随机数,为什么?为什么不...).
I have 2 children, and I want to send signals from children to parent, and an answer (random number, why? why not...) named pipe from the parent to each child.
我有此代码:
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#define WRITE(Str) (void)write(1,Str,strlen(Str))
void handler(int signumber)
{
WRITE("Signal arrived\n");
}
int main(){
/*random number */
srand(time(NULL)); //random number
int r = rand() % 2; //random number between 0 and 1
char original1[]="rdnr: ";
original1[6]=r+'0';
r = rand() % 2;
char original2[]="rdnr: ";
original2[6]=r+'0';
/*pipe, named pipe*/
int pid,fd,fd2;
printf("Fifo start!\n");
int fid=mkfifo("fifo.ftc", S_IRUSR|S_IWUSR ); // creating named pipe file
int fid2=mkfifo("fifo2.ftc", S_IRUSR|S_IWUSR );
if (fid==-1) //error handling
{
printf("Error at fid number: %i",errno);
exit(EXIT_FAILURE);
}
if (fid2==-1) //error handling
{
printf("Error at fid2 number: %i",errno);
exit(EXIT_FAILURE);
}
printf("Pipe system OK!\n");
/*signal*/
sigset_t sigset;
sigemptyset(&sigset); //empty signal set
sigaddset(&sigset,SIGTERM); //SIGTERM is in set
//sigfillset(&sigset); //each signal is in the set
sigprocmask(SIG_BLOCK,&sigset,NULL); //signals in sigset will be blocked
signal(SIGTERM,handler); //signal and handler is connetcted
signal(SIGUSR1,handler);
pid_t child2;
pid_t child=fork();
if (child>0)
{
child2 = fork();
if(child2>0){
printf("Parent, wainting for signal...\n");
sigsuspend(&sigset);
sigprocmask(SIG_UNBLOCK,&sigset,NULL);
int status;
wait(&status);
printf("Parent got 2 signal!\n");
printf("Parent will send 2 random number: %s and %s\n", original1, original2);
fd=open("fifo.ftc",O_WRONLY);
write(fd,original1,12);
close(fd);
fd2=open("fifo2.ftc",O_WRONLY);
write(fd2,original2,12);
close(fd2);
printf("Parent has sent the numbers!\n");
}
else{
printf("I'm child2.\n");
printf("child2 signalnr: %i (it is not blocked)\n", SIGUSR1);
kill(getppid(),SIGUSR1);
/*get pipe*/
sleep(5);
char s[1024]="nothn";
printf("got on pipe, in child2: %d!\n",fid);
fd=open("fifo.ftc",O_RDONLY);
read(fd,s,sizeof(s));
printf("got this on pipe, by child2: %s \n",s);
close(fd);
// remove fifo.ftc
unlink("fifo.ftc");
}
}
else
{
printf("I'm child1.\n");
printf("child1 signal nr: %i (it is blocked)\n",SIGTERM);
sleep(3);
kill(getppid(),SIGTERM);
//sleep(5);
/*get pipe*/
char s[1024]="nothn";
printf("Got this on pipe, by child1: %d!\n",fid2);
fd2=open("fifo2.ftc",O_RDONLY);
read(fd2,s,sizeof(s));
printf("got this inpipe fd2: %s by child2 \n",s);
close(fd2);
// remove fifo2.ftc
unlink("fifo2.ftc");
}
return 0;
}
如果我分别使用它们,但在这里一起使用,则管道和信号可以正常工作.
And the pipes, and the signals work correctly if I use them separately, but together, here, not.
我只有这个:
Fifo start!
Error at fid number: 17
通过错误处理程序.
如何同时正确使用管道和信号?
How can I use correctly the pipes and the signals at the same time?
更新: 我已经按照注释部分中的描述重新考虑了父级,现在看到的输出是:
UPDATE: I've rethinked the parent as was mentioned in the comment section, now the output, what I can see is:
Fifo start!
Pipe system OK!
Parent, wainting for signal...
I'm child2.
I'm child1.
child1 signal nr: 15 (it is blocked)
child2 signalnr: 10 (it is not blocked)
Handled signal nr: 10
Got this on pipe, by child1: 0!
Handled signal nr: 15
got on pipe, in child2: 0!
所以,我所看到的问题是,子进程无法等待管道,我该如何解决呢?
So, the problem as I see is, the child process can't wait for the pipes, how can I solve this?
UPDATE2:
如果我删除
int status;
wait(&status);
然后,来自父级的
可以正常工作,只是什么也无法确保第二个信号在管道事物之前到达.
from the parent then works fine, just nothing is the to ensure the second signal arrives before the pipe things.
推荐答案
您的代码中有一个重复的错误:
One repeating error in your code:
char original1[]="rdnr: ";
original1[6]=r+'0';
sizeof original1
为7,索引6处的字符为字符串的零终止符.通过用r+'0'
覆盖零终止符,您将破坏数组的字符串属性,以便不再可以在其上使用strlen
.
sizeof original1
is 7, the character at index 6 is the zero terminator of the string. By overwriting the zero terminator with r+'0'
you destroy the string property of the array, so that you can no longer use strlen
on it.
修复:
char original1[] = "rdnr: 0";
original1[sizeof original1 - 2] += r;
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