Systemd.Journal

Writing to the journal

sendMessage :: Text -> IO ()

Send a message to the systemd journal.

sendMessage t == sendJournalFields (message t)

sendMessageWith :: Text -> JournalFields -> IO ()

Send a message and supply extra fields.

Note: The MESSAGE field will be replaced with the first parameter to this function. If you don't want this, use sendJournalFields

sendJournalFields :: JournalFields -> IO ()

Send an exact set of fields to the systemd journal.

type JournalFields = HashMap JournalField ByteString

A structured object of all the fields in an entry in the journal. You generally don't construct this yourself, but you use the monoid instance and smart constructors below.

For example,

sendJournalFields (message "Oh god, it burns!" <> priority Emergency)

Standard systemd journal fields

message :: Text -> JournalFields

The human readable message string for this entry. This is supposed to be the primary text shown to the user. It is usually not translated (but might be in some cases), and is not supposed to be parsed for meta data.

messageId :: UUID -> JournalFields

A 128bit message identifier ID for recognizing certain message types, if this is desirable. Developers can generate a new ID for this purpose with journalctl --new-id.

priority :: Priority -> JournalFields

A priority value compatible with syslog's priority concept.

data Priority :: *

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).

Constructors

Emergency

system is unusable

Alert

action must be taken immediately

Critical

critical conditions

Error

error conditions

Warning

warning conditions

Notice

normal but significant condition

Info

informational

Debug

debug-level messages

Instances

Bounded Priority

Enum Priority

Eq Priority

Read Priority

Show Priority

Generic Priority

type Rep Priority = D1 D1Priority ((:+:) ((:+:) ((:+:) (C1 C1_0Priority U1) (C1 C1_1Priority U1)) ((:+:) (C1 C1_2Priority U1) (C1 C1_3Priority U1))) ((:+:) ((:+:) (C1 C1_4Priority U1) (C1 C1_5Priority U1)) ((:+:) (C1 C1_6Priority U1) (C1 C1_7Priority U1))))

codeFile :: FilePath -> JournalFields

The source code file generating this message.

codeLine :: Int -> JournalFields

The source code line number generating this message.

codeFunc :: Text -> JournalFields

The source code function name generating this message.

errno :: Int -> JournalFields

The low-level Unix error number causing this entry, if any. Contains the numeric value of errno(3).

syslogFacility :: Facility -> JournalFields

Syslog compatibility field.

syslogIdentifier :: Text -> JournalFields

Syslog compatibility field.

syslogPid :: CPid -> JournalFields

Syslog compatibility field.

Custom journal fields

data JournalField

Instances

Eq JournalField

Data JournalField

Ord JournalField

Read JournalField

Show JournalField

IsString JournalField

Monoid JournalField

Hashable JournalField

mkJournalField :: Text -> JournalField

Construct a JournalField by converting to uppercase, as required by the journal.

journalField :: JournalField -> Text

Extract the name of a JournalField.

Reading the journal

openJournal

Arguments

:: MonadSafe m

=> [JournalFlag]

A list of flags taken under logical disjunction (or) to specify which journal files to open.

-> Start

Where to begin reading journal entries from.

-> Maybe Filter

An optional filter to apply the journal. Only entries satisfying the filter will be emitted.

-> Maybe Integer

The data field size threshold, or Nothing for no field size limit

-> Producer' JournalEntry m ()

Opens the journal for reading, optionally filtering the journal entries. Filters are defined as arbitrary binary expression trees, which are then rewritten to be in conjunctive normal form before filtering with systemd to comply with systemd's rule system.

data Start

Where to begin reading the journal from.

Constructors

FromStart

Begin reading from the start of the journal.

FromEnd

Begin reading from the end of the journal.

FromCursor JournalEntryCursor

From a JournalEntryCursor.

data JournalEntry

An entry that has been read from the systemd journal.

Instances

Eq JournalEntry

Show JournalEntry

type JournalEntryCursor = ByteString

journalEntryFields :: JournalEntry -> JournalFields

A map of each JournalField to its value.

journalEntryCursor :: JournalEntry -> JournalEntryCursor

A JournalCursor can be used as marker into the journal stream. This can be used to re-open the journal at a specific point in the future, and JournalCursors can be serialized to disk.

journalEntryRealtime :: JournalEntry -> Word64

The time (in microseconds since the epoch) when this journal entry was received by the systemd journal.

data JournalFlag

Flags to specify which journal entries to read.

Constructors

LocalOnly

Only journal files generated on the local machine will be opened.

RuntimeOnly

Only volatile journal files will be opened, excluding those which are stored on persistent storage.

SystemOnly

Only journal files of system services and the kernel (in opposition to user session processes) will be opened.

Instances

Bounded JournalFlag

Enum JournalFlag

Eq JournalFlag

Ord JournalFlag

data Filter

A logical expression to filter journal entries when reading the journal.

Constructors

Match JournalField ByteString

A binary exact match on a given JournalField.

And Filter Filter

Logical conjunction of two filters. Will only show journal entries that satisfy both conditions.

Or Filter Filter

Logical disjunction of two filters. Will show journal entries that satisfy either condition.

Instances

Eq Filter

Data Filter

Show Filter