UNIX环境高级编程学习之第六章系统数据文件和信息 用链表的形式读出一个服务器的远程用户登入登出信息

#pragma pack(1) #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <utmp.h> #include <time.h> #include <arpa/inet.h> struct exit_status_o{ short int a; short int b; }; struct timeval_o{ time_t time; time_t other; }; struct utmpx_o{ char ut_user[32]; char ut_id[4]; char ut_line[32]; int ut_pid; short ut_type; struct exit_status_o ut_exit; struct timeval_o ut_tv; int ut_session; int pad[5]; short ut_syslen; char ut_host[257]; }; struct utmpxs{ struct utmpx_o* data; struct utmpxs* next; }; struct utmpxs * head = NULL; int insertLinklist(struct utmpx_o* data) { if(NULL == head) { head = (struct utmpxs*)malloc(sizeof(struct utmpxs)); head->data = data; head->next = NULL; }else{ struct utmpxs * cur = (struct utmpxs * )malloc(sizeof(struct utmpxs)); cur->data = data; cur->next = head; head = cur; } return 0; } struct utmpx_o* searchLinklist(int pid, char * name) { struct utmpxs * cur = head; while(cur != NULL) { if(cur->data->ut_pid == pid && strcmp(cur->data->ut_user,name) == 0) { return cur->data; } cur = cur->next; } return NULL; } int deleteLinklist(struct utmpx_o* data) { struct utmpxs * up = NULL; struct utmpxs * cur = head; while(cur != NULL) { if(cur->data == data) { free(data); data = NULL; if(up != NULL) { up->next = cur->next; }else{ head = cur->next; } free(cur); cur = NULL; return 0; } up = cur; cur = cur->next; } return -1; } int deleteAllLinklist() { struct utmpxs * cur = head; while(cur != NULL) { head = head->next; free(cur->data); free(cur); cur = head; } return -1; } int main(int argc, char * argv[]) { int fd; int ret; time_t time1; time_t time2; time_t time; fd = open("/home/ubuntu/wtmpx",O_RDONLY); if(fd == -1) { printf("open error/n"); exit(-1); } off_t len; while(1) { struct utmpx_o *up; struct utmpx_o *cur; cur = (struct utmpx_o*)malloc(sizeof(struct utmpx_o)); memset(cur, '/0', sizeof(struct utmpx_o)); ret = read(fd, cur->ut_user, 32); if(ret < 0) { free(cur); break; } ret = read(fd, cur->ut_id, 4); ret = read(fd, cur->ut_line, 32); ret = read(fd, &cur->ut_pid, 4); len = lseek(fd, 0, SEEK_CUR); cur->ut_pid = ntohl(cur->ut_pid); ret = read(fd, &cur->ut_type, 2); cur->ut_type = ntohs(cur->ut_type); ret = read(fd, &cur->ut_exit, 4); len = lseek(fd, 2, SEEK_CUR); ret = read(fd, &cur->ut_tv, 8); ret = read(fd, &cur->ut_session, 4); ret = read(fd, cur->pad, 20); ret = read(fd, &cur->ut_syslen, 2); ret = read(fd, cur->ut_host, 257); len = lseek(fd, 1, SEEK_CUR); if(cur->ut_type ==7) { insertLinklist(cur); }else if(cur->ut_type == 8) { up = searchLinklist(cur->ut_pid, cur->ut_user); if(up != NULL) { time1 = ntohl(up->ut_tv.time); time2 = ntohl(cur->ut_tv.time); time = time2 - time1; printf("pid=%d,user=%s,laytime=%ld, host=%s, time=%s", cur->ut_pid, cur->ut_user, time, cur->ut_host, ctime(&time1)); deleteLinklist(up); }else{ //printf("error/n"); } free(cur); }else{ free(cur); } } close(fd); deleteAllLinklist(); return 0; }