在linux系统下实现了一个多人聊天工具的服务器端和客户端。该工具支持显示在线用户

				#include "global.h"
				
				
				
				
				command cmd_list[MAX_CMD]={
					{"/quit",5,1},
					{"/log",4,2}
				};
				
				
				int check_cmd()
				{
					int i;
					for(i = 0; i < MAX_CMD; i++) { 
						if(!strncmp(cmd_list[i].cmd,key_buffer,cmd_list[i].length))
							return cmd_list[i].num;
					}
					return 0;
				}
				
				
				void do_cmd_log()
				{
					int i = 4;
					int k = 0;
					while(key_buffer[i]==' '||key_buffer[i]
					      =='\t')
						i++;
					if(key_buffer[i] == '\0'||key_buffer[i] == '\n')
						strcpy(filename,"scc.log");
					else {
						while(key_buffer[i]!=' '&&key_buffer[i]
						      !='\t'&& key_buffer[i]!='\n' &&
						      key_buffer[i]!='\0'&&k							filename[k] = key_buffer[i];
							i++;
							k++;
						}
						filename[k] = '\0';
					}
					enable_log = 1;
				}
				
				
				
				void do_cmd(int c)
				{
					switch(c) {
						case 2:
							do_cmd_log();
							break;
						default:
							break;
					}
				}
				
				
				int handle_cmd()
				{
					int c;
					/*if the string is not a command or can't
					 * be handle by client*/
					if(!(c=check_cmd()))
						return -1;
					/*if the command is "quit"*/
					else if(c == 1)
						return 0;
					do_cmd(c);
					return 1;
				}
				
				
				void do_log(char *mes)
				{
					FILE * fp;
					if((fp = fopen(filename,"a")) == NULL) {
						fprintf(stderr,"log file open fail!\n");
						return;
					}
					fprintf(fp,"%s\n",mes);
					fclose(fp);
				}