Linux的那些事儿（7）----系统数据文件和信息

 Date:2009-05-13    09:57:19

Content:系统数据文件和信息

 

一、存取系统数据文件的类似例程

说明	数据文件	头文件	结构	附加的关键字查找函数
passwords	/etc/passwd	<pwd.h>	passwd	getpwnam, getpwuid
groups	/etc/group	<grp.h>	group	getgrnam, getgrgid
shadow	/etc/shadow	<shadow.h>	spwd	getspnam
hosts	/etc/hosts	<netdb.h>	hostent	gethostbyname, gethostbyaddr
networks	/etc/networks	<netdb.h>	netent	getnetbyname, getnetbyaddr
protocols	/etc/protocols	<netdb.h>	protoent	getprotobyname, getprotobynumber
services	/etc/services	<netdb.h>	servent	getservbyname, getservbyport

 

二、函数介绍

1、获取口令文件项目的函数

#include <pwd.h> //成功则返回指针，否则返回NULL struct passwd *getpwuid(uid_t uid); struct passwd *getpwnam(const char *name);

2、查看整个口令文件

#include <pwd.h> struct passwd *getpwent(void); //Returns: pointer if OK, NULL on error or end of file void setpwent(void); void endpwent(void);

3、访问阴影口令文件

#include <shadow.h> //Both return: pointer if OK, NULL on error struct spwd *getspnam(const char *name); struct spwd *getspent(void); void setspent(void); void endspent(void);

4、查看组名或数值组ID

#include <grp.h> //Both return: pointer if OK, NULL on error struct group *getgrgid(gid_t gid); struct group *getgrnam(const char *name);

5、如果需要搜索整个组文件，则需要使用另外几个函数

#include <grp.h> //Returns: pointer if OK, NULL on error or end of file struct group *getgrent(void); void setgrent(void); void endgrent(void);

6、为了获取和设置附加组ID

#include <unistd.h> //Returns: number of supplementary group IDs if OK, 1 on error int getgroups(int gidsetsize, gid_t grouplist[]); //Both return: 0 if OK, 1 on error #include <grp.h> /* on Linux */ #include <unistd.h> /* on FreeBSD, Mac OS X, and Solaris */ int setgroups(int ngroups, const gid_t grouplist[]); #include <grp.h> /* on Linux and Solaris */ #include <unistd.h> /* on FreeBSD and Mac OS X */ int initgroups(const char *username, gid_t basegid);

7、返回与当前主机和操作系统有关的信息

#include <sys/utsname.h> //Returns: non-negative value if OK, 1 on error int uname(struct utsname *name);

8、返回主机名

#include <unistd.h> //Returns: 0 if OK, 1 on error int gethostname(char *name, int namelen);
9、返回当前日期和时间

#include <time.h> time_t time(time_t *calptr);

#include <sys/time.h> int gettimeofday(struct timeval *restrict tp, void *restrict tzp);

#include <time.h> //Both return: pointer to broken-down time struct tm *gmtime(const time_t *calptr); struct tm *localtime(const time_t *calptr);   

#include <time.h> //Returns: calendar time if OK, 1 on error time_t mktime(struct tm *tmptr);

#include <time.h> //Both return: pointer to null-terminated string //Tue Feb 10 18:27:38 2004/n/0 char *asctime(const struct tm *tmptr); char *ctime(const time_t *calptr);

#include <time.h> //Returns: number of characters stored in array if room, 0 otherwise size_t strftime(char *restrict buf, size_t maxsize, const char *restrict format, const struct tm *restrict tmptr);