pid文件

the pid files contains the process id (a number) of a given program. For example, Apache HTTPD may write it's main process number to a pid file - which is a regular text file, nothing more than that -, and later use the information there contained to stop itself. You can also use that information (just do a cat filename.pid) to kill the process yourself, using kill <the number in the .pid file>

/*
 ============================================================================
 Name        : testc.c
 Author      : 
 Version     :
 Copyright   : Your copyright notice
 Description : pid文件的使用，一个终端运行该程序，另一个终端输入 kill -9 `cat testc.pid`
               即可杀死该程序。注意路径和符号``.
 ============================================================================
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

int write_pid(void);

int main(void) {
	printf("Hello World!\n");

	if(write_pid() < 0)
	{
		printf("cannot write pid file!");
		return -1;
	}

	while (1)
	{

	}

	return 0;
}

int write_pid(void)
{
	FILE *f;

	if(!(f = fopen("testc.pid","w")))
	{
		return -1;
	}

	fprintf(f,"%d",(int)getpid());
	fclose(f);

	return 0;
}