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Unix系统（包括linux以及Mac OS X）在程序异常终止后，可能会产生记录当前程序运行信息的core file。可以通过命令ulimit -c n设定core file的大小n KBytes，n为0表示不产生core file，命令行中的设定仅对当前shell有效，若要全局设定，可以在profile文件中写入上述命令。 core file的文件名在不同的系统中不尽相同。在linux系统中，在目录/proc/sys/kernel下的文件core_pattern、core_uses_pid规定了core file的文件名格式，core_uses_pid为1表示core file 文件名使用pid，为0则相反。

可以通过setrlimit()产生core file的大小，getrlimit()获取core file大小的系统设定。编程示范如下：

// Example of usage of getrlimit() and setrlimit()
// luojiahu 2015.8.15

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/resource.h> /* define struct rlimi_t, function getrlimit ... */

int main(void)
{
	struct rlimit t;
	long long softLimit = t.rlim_cur;
	long long hardLimit = t.rlim_max;
	
	printf("original value of struct rlimit\nsoft limit: %lld\nhard limit: %lld\n", softLimit, hardLimit);
	int a = getrlimit(RLIMIT_CORE, &t); /* if get succed, it returns 0, else return -1 */
	if( !a )
	{
		hardLimit = t.rlim_max;
		softLimit = t.rlim_cur;
		printf("current system setting of core file size:\nsoft limit: %lld\nhard limit: %lld\n", softLimit, hardLimit);
	
	}
	else
	{
		perror("get core file system setting failed!\n");
		exit(EXIT_FAILURE);	
	}

	printf("Now setting core file size to:\nsoft limit: 10*1024\nhard limit: 100*1024\n");
	t.rlim_cur = 10*1024;
	t.rlim_max = 100*1024;
	setrlimit(RLIMIT_CORE, &t);
	struct rlimit new_t;
	a = getrlimit(RLIMIT_CORE, &new_t); /* if get succed, it returns 0, else return -1 */
	if( !a )
	{
		hardLimit = new_t.rlim_max;
		softLimit = new_t.rlim_cur;
		printf("current system setting of core file size:\nsoft limit: %lld\nhard limit: %lld\n", softLimit, hardLimit);
	
	}
	else
	{
		exit(EXIT_FAILURE);	
	}
	
//	while(1)
//	{} /* do nothing */	
	return 0;
}

在程序中设定的core file size ，只对当前进程及其子进程有效。可以编写以下程序进行测试（系统设定不产生core file，即ulimit -Sc 0）。执行程序并执行任意其他程序，分别向对应的进程发送信号kill -s signal_number pid，观察是否产生core file。

// This program set core file size in the father process
// fork a child process and test whether a core file will 
// generate when program ended unnormally
// luojiahu 2015.8.16

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/resource.h>
#include <string.h>

#define UNLIMITED 4294967295

void Zero(void* t)
{
	if(t == NULL)
		return ;
	size_t size = sizeof(*t);

	memset(t, 0 , size);
}

int main(void)
{
	unsigned long hardLimit, softLimit;
	struct rlimit coreFileSize;
	Zero(&coreFileSize);
	
	getrlimit(RLIMIT_CORE, &coreFileSize); /* get the system settings */
	hardLimit = (unsigned long)coreFileSize.rlim_max;
	softLimit = (unsigned long)coreFileSize.rlim_cur;
	printf("core file system setting:\nsoft limit: %u\nhard limit: %u\n", softLimit, hardLimit);
	
	printf("Set soft limit to 1000 KB, hard limit to unlimited:\n");
	coreFileSize.rlim_cur = 1000*1024;
	coreFileSize.rlim_max = UNLIMITED;

	setrlimit(RLIMIT_CORE, &coreFileSize);

	pid_t pid = fork();
	if( pid < 0)
	{
		perror("fork faild!\n");
		exit(EXIT_FAILURE);	
	}
	else if( pid == 0)
	{
		printf("this is child process with pid: %d", getpid());
	}
	else
	{
		printf("this is parent process with pid %d", getpid());
	}
	
	while(1)
	{}	/* do nothing */
	
	return 0;
}

以下是对softEtherVPN中函数UnixSetResourceLimit的测试

// This program test the funciont of softEtherVpN
// function void UnixSetResourceLimit(UINT id, UINT64 value)

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/resource.h>
#include <string.h>

#define UINT int
#define UINT64 long long
#define MIN(a, b) ( (a >= b) ? (b) : (a))

void Zero(void *addr, UINT size)
{
	// Validate arguments
	if (addr == NULL || size == 0)
	{
		return;
	}

	// KS
//	KS_INC(KS_ZERO_COUNT);

	memset(addr, 0, size);
}


void UnixSetResourceLimit(UINT id, UINT64 value)
{
	struct rlimit t;
	UINT64 hard_limit;

/*/	if (UnixIs64BitRlimSupported() == false)
	{
		if (value > (UINT64)4294967295ULL)
		{
			value = (UINT64)4294967295ULL;
		}
	}
*/
	Zero(&t, sizeof(t));
	getrlimit(id, &t);

	hard_limit = (UINT64)t.rlim_max;

	Zero(&t, sizeof(t));
	t.rlim_cur = (rlim_t)MIN(value, hard_limit);
	t.rlim_max = (rlim_t)hard_limit;
	setrlimit(id, &t);

	Zero(&t, sizeof(t));
	t.rlim_cur = (rlim_t)value;
	t.rlim_max = (rlim_t)value;
	setrlimit(id, &t);
}

int main(void)
{
	struct rlimit t;
	getrlimit(RLIMIT_CORE, &t);
	printf("core file size system setting:\nsoft limit: %lld\nhard limit: %lld\n", (long long)t.rlim_cur, (long long)t.rlim_max);
	printf("Call functon UnixSetResourceLimit(0)\n");
	UnixSetResourceLimit(RLIMIT_CORE, 0);

	getrlimit(RLIMIT_CORE, &t);
	printf("after funciont call core file size:\nsoft limit: %lld\nhard limit: %lld\n", (long long)t.rlim_cur, (long long)t.rlim_max);

	return 0;
}