Linux的那些事兒（7）—-系統資料檔案和資訊

 Date:2009-05-13    09:57:19

Content:系統資料檔案和資訊

 

一、存取系統資料檔案的類似常式

說明	資料檔案	標頭檔	結構	附加的關鍵字尋找函數
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、函數介紹

1、擷取口令檔案項目的函數

#include <pwd.h><br />//成功則返回指標，否則返回NULL<br />struct passwd *getpwuid(uid_t uid);<br />struct passwd *getpwnam(const char *name);

2、查看整個口令檔案

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

3、訪問陰影口令檔案

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

4、查看組名或數值組ID

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

5、如果需要搜尋整個組檔案，則需要使用另外幾個函數

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

6、為了擷取和設定附加組ID

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

7、返回與當前主機和作業系統有關的資訊

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

8、返回主機名稱

#include <unistd.h><br />//Returns: 0 if OK, 1 on error<br />int gethostname(char *name, int namelen);</p><p>
9、返回當前日期和時間

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

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

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

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

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

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