syslog

syslog

linux c

1. 声明

#include <syslog.h>
void openlog(char*ident,int option ,int facility);
void syslog(int priority,char*format,……)
void closelog()

2. openlog

例子：

openlog(argv[0], LOG_PID, LOG_LOCAL5);

a. openlog会指定一个indent，那么这个程序的每个信息前面都有这个indent，一般是这个程序名。

b. option控制syslog行为：

   option
       The option argument to openlog() is an OR of any of these:

       LOG_CONS       Write directly to system console if there is an error while sending to system logger.

       LOG_NDELAY     Open the connection immediately (normally, the connection is opened when the first message is logged).

       LOG_NOWAIT     Don't  wait  for  child  processes that may have been created while logging the message.  (The GNU C library does not create a child
                      process, so this option has no effect on Linux.)

       LOG_ODELAY     The converse of LOG_NDELAY; opening of the connection is delayed until syslog() is called.  (This is the default, and  need  not  be
                      specified.)

       LOG_PERROR     (Not in POSIX.1-2001 or POSIX.1-2008.)  Print to stderr as well.

       LOG_PID        Include PID with each message.

c. The facility argument is used to specify what type of program is logging the message. This lets the configuration file specify that messages from different facilities will be handled differently.

配置文件是/etc/syslog.conf，可以配置不同程序类型，保存不同的位置：

kern.*                  /var/log/kern.log
user.*                  /var/log/syslog
local2.*                /var/log/network.log
local3.*                /var/log/onvif.log
local5.*                /var/log/media.log
local6.*                /var/log/rtspd.log

3. syslog

例子：

syslog(LOG_DEBUG, "This is test message %s\n", argv[0]);

第一个参数是level，表示消息的重要性，syslog man page里关于level的选项，从上往下重要性逐渐下降。

   level
       This determines the importance of the message.  The levels are, in order of decreasing importance:

       LOG_EMERG      system is unusable

       LOG_ALERT      action must be taken immediately

       LOG_CRIT       critical conditions

       LOG_ERR        error conditions

       LOG_WARNING    warning conditions

       LOG_NOTICE     normal, but significant, condition

       LOG_INFO       informational message

       LOG_DEBUG      debug-level message

后面的参数就是fmt与参数。

4. closelog

closelog()关闭描述符。是否使用是可选的。