long* find_pid_by_name( char* pidName)
{
	DIR *dir;
	struct dirent *next;
	long* pidList=NULL;
	int i=0;

        ///proc中包括当前的进程信息,读取该目录
	dir = opendir("/proc");
	if (!dir)
		perror_msg_and_die("Cannot open /proc");
	
        //遍历
	while ((next = readdir(dir)) != NULL) {
		FILE *status;
		char filename[READ_BUF_SIZE];
		char buffer[READ_BUF_SIZE];
		char name[READ_BUF_SIZE];

		/* Must skip ".." since that is outside /proc */
		if (strcmp(next->d_name, "..") == 0)
			continue;

		/* If it isn't a number, we don't want it */
		if (!isdigit(*next->d_name))
			continue;
                //设置进程
		sprintf(filename, "/proc/%s/status", next->d_name);
		if (! (status = fopen(filename, "r")) ) {
			continue;
		}
		if (fgets(buffer, READ_BUF_SIZE-1, status) == NULL) {
			fclose(status);
			continue;
		}
		fclose(status);

                //得到进程id
		/* Buffer should contain a string like "Name:   binary_name" */
		sscanf(buffer, "%*s %s", name);
		if (strcmp(name, pidName) == 0) {
			pidList=realloc( pidList, sizeof(long) * (i+2));
			pidList[i++]=strtol(next->d_name, NULL, 0);
		}
	}

	if (pidList) {
		pidList[i]=0;
	}
	return NULL;
}