sd_journal_get_usage — Journal disk usage
#include <systemd/sd-journal.h>
| int sd_journal_get_usage( | sd_journal* j, | 
| uint64_t* bytes ); | 
sd_journal_get_usage()
                determines the total disk space currently used by
                journal files (in bytes). If
                SD_JOURNAL_LOCAL_ONLY was passed
                when opening the journal this value will only reflect
                the size of journal files of the local host, otherwise
                of all hosts.
The sd_journal_get_usage()
                interface is available as shared library, which can be
                compiled and linked to with the
                libsystemd-journal
                pkg-config(1)
                file.