Log messages are prioritized.

Note that the Enum instance for this class is incomplete. We abuse toEnum and fromEnum to map these constructors to their corresponding bit-mask value in C, but not all uses cases provided by of enumerating that class are fully supported (issue #5).

Syslog distinguishes various system facilities. Most applications should log in USER.

Options for the syslog service. Set with withSyslog.

Bracket an IO computation between calls to _openlog, _setlogmask, and _closelog. The function can be used as follows:

main = withSyslog "my-ident" [PID, PERROR] USER (logUpTo Debug) $ do
         putStrLn "huhu"
         syslog Debug "huhu"

Note that these are process-wide settings, so multiple calls to this function will interfere with each other in unpredictable ways.

Log a message with the given priority.

Note that the API of this function is somewhat unsatisfactory and is likely to change in the future:

1. The function should accept a [Facility] argument so that messages can be logged to certain facilities without depending on the process-wide global default value set by openlog (issue #6).
2. The Priority argument should be [Priority].
3. Accepting a ByteString instead of String would be preferrable because we can log those more efficiently, i.e. without marshaling. On top of that, we can provide a wrapper for this function that accepts anything that can be marshaled into a ByteString (issue #7).

Returns the list of priorities up to and including the argument. Note that the syslog priority Debug is considered the highest one in this context, which may counter-intuitive for some.

>>> logUpTo(Debug)
[Emergency,Alert,Critical,Error,Warning,Notice,Info,Debug]

>>> logUpTo(Emergency)
[Emergency]

Escape any occurances of '%' in a string, so that it is safe to pass it to _syslog. The syslog wrapper does this automatically.

Unfortunately, the application of this function to every single syslog message is a performence nightmare. Instead, we should call syslog the existence of this function is a kludge, in a way that doesn't require any escaping (issue #8).

Open a connection to the system logger for a program. The string identifier passed as the first argument is prepended to every message, and is typically set to the program name. The behavior is unspecified by POSIX.1-2008 if that identifier is nullPtr.

Close the descriptor being used to write to the system logger.

A process has a log priority mask that determines which calls to syslog may be logged. All other calls will be ignored. Logging is enabled for the priorities that have the corresponding bit set in mask. The initial mask is such that logging is enabled for all priorities. This function sets this logmask for the calling process, and returns the previous mask. If the mask argument is 0, the current logmask is not modified.

Generate a log message, which will be distributed by syslogd(8). The priority argument is formed by ORing the facility and the level values (explained below). The remaining arguments are a format, as in printf(3) and any arguments required by the format, except that the two character sequence %m will be replaced by the error message string strerror(errno). A trailing newline may be added if needed.