使用syslog()函数处理日志信息

函数声明：#include <syslog.h>void syslog(int priority, const char *message, arguments...);priority参数的格式（severity level|facility code）示例： LOG_ERR|LOG_USERseverity level：Priority Level               DescriptionLOG_EMERG                    An emergency situationLOG_ALERT                    High-priority problem, such as database corruptionLOG_CRIT                     Critical error, such as hardware failureLOG_ERR                      ErrorsLOG_WARNING                  WarningLOG_NOTICE                   Special conditions requiring attentionLOG_INFO                     Informational messagesLOG_DEBUG                    Debug messagesfacility value（转自syslog.h头文件）：/* facility codes */#define LOG_KERN        (0<<3)  /* kernel messages */#define LOG_USER        (1<<3)  /* random user-level messages */#define LOG_MAIL        (2<<3)  /* mail system */#define LOG_DAEMON      (3<<3)  /* system daemons */#define LOG_AUTH        (4<<3)  /* security/authorization messages */#define LOG_SYSLOG      (5<<3)  /* messages generated internally by syslogd */#define LOG_LPR         (6<<3)  /* line printer subsystem */#define LOG_NEWS        (7<<3)  /* network news subsystem */#define LOG_UUCP        (8<<3)  /* UUCP subsystem */#define LOG_CRON        (9<<3)  /* clock daemon */#define LOG_AUTHPRIV    (10<<3) /* security/authorization messages (private) */#define LOG_FTP         (11<<3) /* ftp daemon */示例代码：#include <syslog.h>#include <stdio.h>int main(void){        FILE *f;        f = fopen("abc","r");        if(!f)                                                    syslog(LOG_ERR|LOG_USER,"test - %m\n");       }

上面的日志信息由系统自动给出，我们也可过滤日志信息。用到以下函数：

#include <syslog.h>void closelog(void);void openlog(const char *ident, int logopt, int facility);int setlogmask(int maskpri);logopt参数的选项：logopt Parameter    DescriptionLOG_PID             Includes the process identifier, a unique number allocated to each process by the system, in the messages.LOG_CONS            Sends messages to the console if they can’t be logged.LOG_ODELAY          Opens the log facility at first call to .LOG_NDELAY          Opens the log facility immediately, rather than at first log.示例代码：#include <syslog.h>#include <stdio.h>#include <unistd.h>int main(void){        int logmask;        openlog("logmask", LOG_PID|LOG_CONS, LOG_USER); /*日志信息会包含进程id。*/        syslog(LOG_INFO, "informative message, pid=%d", getpid());         syslog(LOG_DEBUG,"debug message, should appear");   /*记录该日志信息。*/        logmask = setlogmask(LOG_UPTO(LOG_NOTICE));     /*设置屏蔽低于NOTICE级别的日志信息。*/        syslog(LOG_DEBUG, "debug message, should not appear");  /*该日志信息被屏蔽，不记录。*/}

不同安全级别的日志信息存放在/var/log目录下的哪个文件中是由/etc/syslog.conf文件控制的，下面是我系统中syslog.conf文件的内容：

#  /etc/syslog.conf     Configuration file for syslogd.##                       For more information see syslog.conf(5)#                       manpage.## First some standard logfiles.  Log by facility.#auth,authpriv.*                 /var/log/auth.log*.*;auth,authpriv.none          -/var/log/syslog#cron.*                         /var/log/cron.logdaemon.*                        -/var/log/daemon.logkern.*                          -/var/log/kern.loglpr.*                           -/var/log/lpr.logmail.*                          -/var/log/mail.loguser.*                          -/var/log/user.loguucp.*                          /var/log/uucp.log## Logging for the mail system.  Split it up so that# it is easy to write scripts to parse these files.#mail.info                       -/var/log/mail.infomail.warn                       -/var/log/mail.warnmail.err                        /var/log/mail.err# Logging for INN news system#news.crit                       /var/log/news/news.critnews.err                        /var/log/news/news.errnews.notice                     -/var/log/news/news.notice## Some `catch-all' logfiles.#*.=debug;\        auth,authpriv.none;\        news.none;mail.none     -/var/log/debug*.=info;*.=notice;*.=warn;\        auth,authpriv.none;\        cron,daemon.none;\        mail,news.none          -/var/log/messages## Emergencies are sent to everybody logged in.#*.emerg                         *## I like to have messages displayed on the console, but only on a virtual# console I usually leave idle.##daemon,mail.*;\#       news.=crit;news.=err;news.=notice;\#       *.=debug;*.=info;\#       *.=notice;*.=warn       /dev/tty8# The named pipe /dev/xconsole is for the `xconsole' utility.  To use it,# you must invoke `xconsole' with the `-file' option:##    $ xconsole -file /dev/xconsole [...]## NOTE: adjust the list below, or you'll go crazy if you have a reasonably#      busy site..#daemon.*;mail.*;\        news.crit;news.err;news.notice;\        *.=debug;*.=info;\        *.=notice;*.=warn       |/dev/xconsole实例代码：

1 #include <string>
      2 #include<iostream>
      3 #include<algorithm>
      4 #include<list>
      5 #include<syslog.h>
      6 using namespacestd ;
      7
      8 //===============================================

      9
     10 class TLOG
     11 {
     12 public:
     13 TLOG();
     14 ~TLOG();
     15 TLOG& operator<<(const char * p ) ;
     16 TLOG& operator<<(string & s ) ;
     17 TLOG& operator<<( TLOG&(* pfun)(TLOG&)) ;
     18
     19 void debug(const char * p ) ;
     20 void debug(string & s ) ;
     21
     22 void log(const char * p ) ;
     23 void log(string & s ) ;
     24 } ;
     25 TLOG& endl( TLOG& object) ;
     26
     27 const char* LOG_PREFIX ="root_log : " ;
     28
     29 TLOG glog ;
     30
     31 TLOG::TLOG()
     32 {
     33 #ifdef LOG_SYSLOGD
     34 openlog( LOG_PREFIX, LOG_PID, LOG_USER) ;
 35 #endif
     36 }
     37 TLOG::~TLOG()
     38 {
     39 #ifdef LOG_SYSLOGD
     40 closelog();
     41 #endif
     42 }
     43
     44 TLOG& TLOG::operator<<(const char * p )
     45 {
     46 #ifdef LOG_STDOUT
     47 cout << p;
     48 #endif
     49 return *this;
     50 }
     51
     52 TLOG& TLOG::operator<<(string & s )
     53 {
     54 #ifdef LOG_STDOUT
     55 cout << s;
     56 #endif
     57 return *this;
     58 }
     59 TLOG& TLOG::operator<<( TLOG& (* pfun)(TLOG&))
     60 {
     61 return pfun(*this);
     62 }
     63 TLOG& endl( TLOG& object)
     64 {
     65 #ifdef LOG_STDOUT
     66 cout <<endl ;
     67 #endif
     68 return object ;
69 }
     70
     71 void TLOG::debug(const char * p )
     72 {
     73 *this<< p ;
     74 return ;
     75 }
     76 void TLOG::debug(string & s )
     77 {
     78 *this<< s ;
     79 return ;
     80 }
     81
     82 void TLOG::log(const char * p )
     83 {
     84 *this<< LOG_PREFIX<< p << endl;
     85
     86 #ifdef LOG_SYSLOG
     87 syslog( LOG_INFO, p) ;
     88 #endif
     89 return ;
     90 }
     91 void TLOG::log(string & s )
     92 {
     93 *this<< LOG_PREFIX<< s << endl;
     94
     95 #ifdef LOG_SYSLOG
     96 syslog( LOG_INFO, s.c_str()) ;
     97 #endif
     98 return ;
     99 }
    100
    101 int
    102 main(void)
103 {
    104 glog.log("abcde");
    105 // glog.debug(__func__);

    106 string word;
    107 cout<<"Enter a line:";
    108 cin>>word;
    109 while(cin.get()!='\n')
    110 continue;
    111 cout<<word<<"is all"<<"wanted!\n";
    112
    113 string line;
    114 cout<<"Enter a line:(really)";
    115 getline(cin,line);
    116 cout<<"line:"<<line<<endl;
    117 return 0;
    118 }

结果：

 

ct 16 16:01:42 zerk a.out: abcde