Linux Syslog Learning

Most of the things that have been related to watching lighttpd facgi. See the following sample code on the LIGHTTPD website.

#include <stdlib.h> #include <string.h> #include <syslog.h> #include <alloca.h> #include < fcgiapp.h> #define Listensock_fileno 0#define listensock_flags 0int Main (int argc, char** argv) {openlog ("testfastcgi ", log_cons|  Log_ndelay, Log_user); int err = Fcgx_init ();  /* Call before Accept in multithreaded apps */if (err) {syslog (Log_info, "Fcgx_init failed:%d", err); return 1;}  Fcgx_request CGI;  Err = Fcgx_initrequest (&cgi, Listensock_fileno, listensock_flags);  if (err) {syslog (Log_info, "Fcgx_initrequest failed:%d", err); return 2;}    while (1) {err = Fcgx_accept_r (&cgi);    if (err) {syslog (Log_info, "Fcgx_accept_r stopped:%d", err);    char** envp;    int size = 200;    for (envp = CGI.ENVP; *envp; ++envp) Size + = strlen (*ENVP) + 11;    char* result = (char*) alloca (size);    strcpy (Result, "status:200 ok\r\ncontent-type:text/html\r\n\r\n"); strcat (Result, "
This fastcgi process is to output log to the syslog. The syslog was not very well understood, and it was then checked. Syslog is primarily a log system for Linux. There are mainly the following 3 Api:openlog,syslog and Closelog for the user process to write some log to the corresponding system log.
void Openlog (const char *ident, int option, int facility);
Function Description: Open the log device for reading and writing, similar to the open file system call; calling Openlog is optional. If you do not call Openlog, the Openlog is called automatically when you first call the syslog.
Parameter description:
Ident: is a token, the string represented by ident will be fixed in front of each line of the log to identify the log, usually written as the name of the current program for marking.
Option
Specifies the control flags for the Openlog function and the syslog function that is called next. You can take the following values:
Log_cons If an error occurs when sending information to the SYSLOGD daemon, output the relevant information directly to the terminal
Log_ndelay immediately open a connection to the system log (typically, the connection to the log system is turned on only if the first log information is generated)
Log_odelay is similar to the Log_ndelay parameter, and the connection to the system log is created only when the syslog function is called
Log_perror sends information to the standard error output while writing information to the log
Log_pid Each log message contains the process number
Facility: Specifies the type of message program to record, corresponding to facility in the configuration file syslog.conf of the syslogd daemon. The following values are desirable:
Log_auth Authentication System (login, Su, Getty, etc.)
Log_authpriv with Log_auth but only log in to a single user-readable file of your choice. Log_cron CRON Daemon
Log_daemon Other system daemons, such as routed
Log_ftp File Transfer Protocol: FTPD, TFTPD
Log_kern kernel-generated messages
LOG_LPR System Printer Buffer pool: LPR, LPD
Log_mail e-mail system
Log_news Network News System
Log_syslog internal messages generated by SYSLOGD (8)
Log_user messages generated by random user processes
LOG_UUCP UUCP Subsystem
LOG_LOCAL0 ~ LOG_LOCAL7 local use reserved
void syslog (int priority, const char *format, ...);
Function Description: Writes a log similar to the file system call to write.
Priority: Represents the level of the message, corresponding to the levels in the configuration file syslog.conf of the syslogd daemon. The following values are desirable:
Log_emerg Emergency situation
Log_alert should be immediately corrected for problems such as system database corruption
Log_crit important situations, such as hard drive errors
Log_err Error
Log_warning warning message
Log_notice is not an error condition, but may need to be handled
Log_info Intelligence Error
Log_debug contains information about intelligence, which is usually used when debugging a program
void Closelog ();
Function Description: Turn off the log device, similar to the file system call Close; Call Closelog is also optional, it simply closes the descriptor that is used to communicate with the syslog daemon.
Since I first learned about the syslog, I don't know where the log output of the fastcgi process is. I checked the output to/var/log/messages. However, there are no messages files in this directory.
This is because the config file for syslog is not configured.
The/etc/syslog.conf file is a configuration file for the Linux journaling system. (under Ubuntu for/etc/rsyslog.d/50-default.conf)
Edit/etc/rsyslog.d/50-default.conf
One of them has such a *.=info;*.=notice;*.=warn;\ auth,authpriv.none;\ cron,daemon.none;\ mail,news.none-/var/log/messa Ges This is already there, but it is commented (some options are commented like Log_user). Now the annotation is OK. Then restart the Syslog:sudo service rsyslog restart (sudo restart rsyslog).
Linux Syslog Learning