学步园

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_USER

severity level：

Priority Level               Description

LOG_EMERG                    An emergency situation

LOG_ALERT                    High-priority problem, such as database corruption

LOG_CRIT                     Critical error, such as hardware failure

LOG_ERR                      Errors

LOG_WARNING                  Warning

LOG_NOTICE                   Special conditions requiring attention

LOG_INFO                     Informational messages

LOG_DEBUG                    Debug messages

facility 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    Description

LOG_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.log

daemon.*                        -/var/log/daemon.log

kern.*                          -/var/log/kern.log

lpr.*                           -/var/log/lpr.log

mail.*                          -/var/log/mail.log

user.*                          -/var/log/user.log

uucp.*                          /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.info

mail.warn                       -/var/log/mail.warn

mail.err                        /var/log/mail.err

# Logging for INN news system

#

news.crit                       /var/log/news/news.crit

news.err                        /var/log/news/news.err

news.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：

结果：