13th Chapter The Guardian process summary

1 Writing daemon Basic rules

1) umake (0) Set the file mode creation screen Word to 0

2) after fork, the parent process exit

3) Child process call Setsid

4) Change the working directory ChDir ("/")

5) Close all open file descriptors

6) Open file descriptor on/dev/null

2 Daemon Process error handling

Three ways to generate log messages:

1) kernel process Call log function write log message to/dev/klog

2) User process calls Syslog function write log message to/dev/log

3) The process on the network host sends a log message UDP packet to 514 port

The syslogd daemon is used to process log messages, and the profile for this process is typically/etc/syslog.conf, which determines how different kinds of messages should be handled

#include <syslog.h>void openlog (constchar *ident,int option,int facility) void syslog (int priority,constchar *format,...) void Closelog (); int setlogmask (int maskpri)

Ident is typically the program name and will be added to each log message

13th Chapter The Guardian process summary