我对bgwriter.c 与 guc 关系的初步理解

我用例子来说明：只是一个模拟，我自己做的 假的 bgwriter.c

[root@localhost test]# cat bgwriter.c

#include<stdio.h>

#include<stdlib.h>

#include<signal.h>

#include "bgwriter.h"

#include "guc.h"

//some conditions make it change, eg:signal

int BgWriterDelay=100;

void sighandler(int sig);

int main()

{

 

  signal(SIGHUP,sighandler);

  for (;;)

  {

    sleep(1);

  }

}

void sighandler(int sig)

{

  changeDelay();

  fprintf(stderr,"BgWriterDelay is now %d.\n",BgWriterDelay);

  //here I just want to demo, so close it

  exit(0);

}

[root@localhost test]#

/////////////////////////////////////////////////////////////////

下面的 "bgwriter.h" and "guc.h" and "guc.c"，也都是假的。只是为了模拟。
/////////////////////////////////////////////////////////////////

[root@localhost test]# cat bgwriter.h

extern int BgWriterDelay;

[root@localhost test]#



[root@localhost test]# cat guc.h

extern void changeDelay();

[root@localhost test]#cat guc.c

#include "bgwriter.h"

void changeDelay()

{

  //to simulate reading configuration file etc.

  BgWriterDelay=500;

}

[root@localhost test]#

 

/////////////////////////////////////////////////////////////////

给 SIGHUP 信号

 

[root@localhost test]# gcc bgwriter.c guc.c -o bgwriter.o

[root@localhost test]# ./bgwriter.o

[root@localhost ~]# ps -ef|grep bgwriter.o

root      5475  5297  0 15:08 pts/6    00:00:00 ./bgwriter.o

root      5500  5479  0 15:08 pts/7    00:00:00 grep bgwriter.o

[root@localhost ~]# kill -s SIGHUP 5475

[root@localhost ~]#

BgWriterDelay is now 500.

[root@localhost test]#

结束：