Module: Systemd::Journal::Navigable

Included in:
Systemd::Journal
Defined in:
lib/systemd/journal/navigable.rb

Instance Method Summary collapse

Instance Method Details

#cursor ⇒ String

returns a string representing the current read position. This string can be passed to #seek or #cursor?.

Returns:

  • (String) —

    a cursor token.



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# File 'lib/systemd/journal/navigable.rb', line 10

def cursor
  out_ptr = FFI::MemoryPointer.new(:pointer, 1)
  if (rc = Native.sd_journal_get_cursor(@ptr, out_ptr)) < 0
    raise JournalError, rc
  end

  Journal.read_and_free_outstr(out_ptr.read_pointer)
end

#cursor?(c) ⇒ Boolean

Check if the read position is currently at the entry represented by the provided cursor value. provided cursor, False otherwise.

Parameters:

  • c (String) —

    a cursor token returned from #cursor.

Returns:

  • (Boolean) —

    True if current entry is the one represented by the



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# File 'lib/systemd/journal/navigable.rb', line 24

def cursor?(c)
  if (rc = Native.sd_journal_test_cursor(@ptr, c)) < 0
    raise JournalError, rc
  end

  rc > 0
end

#move(offset = 1) ⇒ Integer

Move the read pointer by ‘offset` entries.

Parameters:

  • offset (Integer) (defaults to: 1) —

    how many entries to move the read pointer by. If this value is positive, the read pointer moves forward. Otherwise, it moves backwards. Defaults to moving forward one entry.

Returns:

  • (Integer) —

    number of entries the read pointer actually moved.



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# File 'lib/systemd/journal/navigable.rb', line 37

def move(offset = 1)
  (offset > 0) ? move_next_skip(offset) : move_previous_skip(-offset)
end

#move_next ⇒ Boolean

Move the read pointer to the next entry in the journal.

Returns:

  • (Boolean) —

    True if moving to the next entry was successful.

  • (Boolean) —

    False if unable to move to the next entry, indicating that the pointer has reached the end of the journal.



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# File 'lib/systemd/journal/navigable.rb', line 45

def move_next
  with_auto_reopen {
    rc = Native.sd_journal_next(@ptr)
    raise JournalError, rc if rc < 0
    rc > 0
  }
end

#move_next_skip(amount) ⇒ Integer

Move the read pointer forward by ‘amount` entries.

Returns:

  • (Integer) —

    actual number of entries by which the read pointer moved. If this number is less than the requested amount, the read pointer has reached the end of the journal.



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# File 'lib/systemd/journal/navigable.rb', line 57

def move_next_skip(amount)
  with_auto_reopen {
    rc = Native.sd_journal_next_skip(@ptr, amount)
    raise JournalError, rc if rc < 0
    rc
  }
end

#move_previous ⇒ Boolean

Move the read pointer to the previous entry in the journal.

Returns:

  • (Boolean) —

    True if moving to the previous entry was successful.

  • (Boolean) —

    False if unable to move to the previous entry, indicating that the pointer has reached the beginning of the journal.



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# File 'lib/systemd/journal/navigable.rb', line 69

def move_previous
  with_auto_reopen {
    rc = Native.sd_journal_previous(@ptr)
    raise JournalError, rc if rc < 0
    rc > 0
  }
end

#move_previous_skip(amount) ⇒ Integer

Move the read pointer backwards by ‘amount` entries.

Returns:

  • (Integer) —

    actual number of entries by which the read pointer was moved. If this number is less than the requested amount, the read pointer has reached the beginning of the journal.



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# File 'lib/systemd/journal/navigable.rb', line 81

def move_previous_skip(amount)
  with_auto_reopen {
    rc = Native.sd_journal_previous_skip(@ptr, amount)
    raise JournalError, rc if rc < 0
    rc
  }
end

#seek(where) ⇒ True

Seek to a position in the journal. Note: after seeking, you must call #move_next or #move_previous

before you can call {#read_field} or {#current_entry}.
When calling `seek(:tail)` the read pointer is positioned _after_
the last entry in the journal -- thus you should use `move_previous`.
Otherwise, use `move_next`.

Examples:

Read last journal entry

j = Systemd::Journal.new
j.seek(:tail)
j.move_previous
puts j.current_entry

Parameters:

  • whence (Symbol, Time) —

    one of :head, :tail, or a Time instance. ‘:head` (or `:start`) will seek to the beginning of the journal. `:tail` (or `:end`) will seek to the end of the journal. When a `Time` is provided, seek to the journal entry logged closest to that time. When a String is provided, assume it is a cursor from #cursor and seek to that entry.

Returns:

  • (True)

Raises:



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# File 'lib/systemd/journal/navigable.rb', line 108

def seek(where)
  rc = if [:head, :start].include?(where)
    Native.sd_journal_seek_head(@ptr)
  elsif [:tail, :end].include?(where)
    Native.sd_journal_seek_tail(@ptr)
  elsif where.is_a?(Time)
    Native.sd_journal_seek_realtime_usec(
      @ptr,
      where.to_i * 1_000_000
    )
  elsif where.is_a?(String)
    Native.sd_journal_seek_cursor(@ptr, where)
  else
    raise ArgumentError, "Unknown seek type: #{where.class}"
  end

  raise JournalError, rc if rc < 0

  true
end