| $LOG_EMERG | LOG_EMERG | System is unusable | |
| $LOG_ALERT | LOG_ALERT | Immediate action required | |
| $LOG_CRIT | LOG_CRIT | Critical conditions | |
| $LOG_ERR | LOG_ERR | | |
| $LOG_WARNING | LOG_WARNING | | |
| $LOG_NOTICE | LOG_NOTICE | | |
| $LOG_INFO | LOG_INFO | | |
| $LOG_DEBUG | LOG_DEBUG | | |
| $LOG_KERN | LOG_KERN | | |
| $LOG_USER | LOG_USER | Genetic user level | |
| $LOG_MAIL | LOG_MAIL | Log to email | |
| $LOG_DAEMON | LOG_DAEMON | Other system daemons | |
| $LOG_AUTH | LOG_AUTH | | |
| $LOG_SYSLOG | LOG_SYSLOG | | Not available on Netware |
| $LOG_LPR | LOG_LPR | | |
| $LOG_NEWS | LOG_NEWS | Usenet new | Not available on HP-UX |
| $LOG_CRON | LOG_CRON | | Not available on all platforms |
| $LOG_AUTHPRIV | LOG_AUTHPRIV | | Not available on AIX |
| $LOG_LOCAL0 | LOG_LOCAL0 | | Not available on Windows and Netware |
| $LOG_LOCAL1 | LOG_LOCAL1 | | Not available on Windows and Netware |
| $LOG_LOCAL2 | LOG_LOCAL2 | | Not available on Windows and Netware |
| $LOG_LOCAL3 | LOG_LOCAL3 | | Not available on Windows and Netware |
| $LOG_LOCAL4 | LOG_LOCAL4 | | Not available on Windows and Netware |
| $LOG_LOCAL5 | LOG_LOCAL5 | | Not available on Windows and Netware |
| $LOG_LOCAL6 | LOG_LOCAL6 | | Not available on Windows and Netware |
| $LOG_LOCAL7 | LOG_LOCAL7 | | Not available on Windows and Netware |
| $LOG_PID | LOG_PID | | |
| $LOG_CONS | LOG_CONS | | |
| $LOG_ODELAY | LOG_ODELAY | | |
| $LOG_NDELAY | LOG_NDELAY | | |
| $LOG_NOWAIT | LOG_NOWAIT | | Not available on BeOS |
| $LOG_PERROR | LOG_PERROR | | Not available on AIX |