Description¶

sd_journal_open() opens the log journal for reading. It will find all journal files automatically and interleave them automatically when reading. As first argument it takes a pointer to a sd_journal pointer, which on success will contain journal context object afterwards. The second argument is a flags field, which may consist of the following flags ORed together: SD_JOURNAL_LOCAL_ONLY makes sure only journal files generated on the local machine will be opened. SD_JOURNAL_RUNTIME_ONLY makes sure only volatile journal files will be opened, excluding those which are stored on persistent storage. SD_JOURNAL_SYSTEM_ONLY will ensure that only journal files of system services and the kernel (in opposition to user session processes) will be opened.

sd_journal_open_directory() is similar to sd_journal_open() but takes an absolute directory path as argument. All journal files in this directory will be opened and interleaved automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently understood for this call.

sd_journal_close() will close the journal context allocated with sd_journal_open() or sd_journal_open_directory() and free its resources.

When opening the journal only journal files accessible to the calling user will be opened. If journal files are not accessible to the caller this will be silently ignored.

See sd_journal_next(3) for an example how to iterate through the journal after opening it with sd_journal_open().

A journal context object returned by sd_journal_open() references a specific journal entry as current entry, similar to a file seek index in a classic file system file, but without absolute positions. It may be altered with sd_journal_next(3) and sd_journal_seek_head(3) and related calls. The current entry position may be exported in cursor strings, as accessible via sd_journal_get_cursor(3). Cursor strings may be used to globally identify a specific journal entry in a stable way and then later to seek to it (or if the specific entry is not available locally, to its closest entry in time) sd_journal_seek_cursor(3).

Notification of journal changes is available via sd_journal_get_fd() and related calls.

Return Value¶

The sd_journal_open() and sd_journal_open_directory() calls return 0 on success or a negative errno-style error code. sd_journal_close() returns nothing.

Notes¶

The sd_journal_open(), sd_journal_open_directory() and sd_journal_close() interfaces are available as shared library, which can be compiled and linked to with the libsystemd-journal pkg-config(1) file.

See Also¶

systemd(1), sd-journal(3), sd_journal_next(3), sd_journal_get_data(3)