1SD_JOURNAL_OPEN(3)              sd_journal_open             SD_JOURNAL_OPEN(3)
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NAME

6       sd_journal_open, sd_journal_open_directory,
7       sd_journal_open_directory_fd, sd_journal_open_files,
8       sd_journal_open_files_fd, sd_journal_close, sd_journal,
9       SD_JOURNAL_LOCAL_ONLY, SD_JOURNAL_RUNTIME_ONLY, SD_JOURNAL_SYSTEM,
10       SD_JOURNAL_CURRENT_USER, SD_JOURNAL_OS_ROOT - Open the system journal
11       for reading
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SYNOPSIS

14       #include <systemd/sd-journal.h>
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16       int sd_journal_open(sd_journal **ret, int flags);
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18       int sd_journal_open_directory(sd_journal **ret, const char *path,
19                                     int flags);
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21       int sd_journal_open_directory_fd(sd_journal **ret, int fd, int flags);
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23       int sd_journal_open_files(sd_journal **ret, const char **paths,
24                                 int flags);
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26       int sd_journal_open_files_fd(sd_journal **ret, int fds[],
27                                    unsigned n_fds, int flags);
28
29       void sd_journal_close(sd_journal *j);
30

DESCRIPTION

32       sd_journal_open() opens the log journal for reading. It will find all
33       journal files automatically and interleave them automatically when
34       reading. As first argument it takes a pointer to a sd_journal pointer,
35       which, on success, will contain a journal context object. The second
36       argument is a flags field, which may consist of the following flags
37       ORed together: SD_JOURNAL_LOCAL_ONLY makes sure only journal files
38       generated on the local machine will be opened.  SD_JOURNAL_RUNTIME_ONLY
39       makes sure only volatile journal files will be opened, excluding those
40       which are stored on persistent storage.  SD_JOURNAL_SYSTEM will cause
41       journal files of system services and the kernel (in opposition to user
42       session processes) to be opened.  SD_JOURNAL_CURRENT_USER will cause
43       journal files of the current user to be opened. If neither
44       SD_JOURNAL_SYSTEM nor SD_JOURNAL_CURRENT_USER are specified, all
45       journal file types will be opened.
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47       sd_journal_open_directory() is similar to sd_journal_open() but takes
48       an absolute directory path as argument. All journal files in this
49       directory will be opened and interleaved automatically. This call also
50       takes a flags argument. The flags parameters accepted by this call are
51       SD_JOURNAL_OS_ROOT, SD_JOURNAL_SYSTEM, and SD_JOURNAL_CURRENT_USER. If
52       SD_JOURNAL_OS_ROOT is specified, journal files are searched for below
53       the usual /var/log/journal and /run/log/journal relative to the
54       specified path, instead of directly beneath it. The other two flags
55       limit which files are opened, the same as for sd_journal_open().
56
57       sd_journal_open_directory_fd() is similar to
58       sd_journal_open_directory(), but takes a file descriptor referencing a
59       directory in the file system instead of an absolute file system path.
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61       sd_journal_open_files() is similar to sd_journal_open() but takes a
62       NULL-terminated list of file paths to open. All files will be opened
63       and interleaved automatically. This call also takes a flags argument,
64       but it must be passed as 0 as no flags are currently understood for
65       this call. Please note that in the case of a live journal, this
66       function is only useful for debugging, because individual journal files
67       can be rotated at any moment, and the opening of specific files is
68       inherently racy.
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70       sd_journal_open_files_fd() is similar to sd_journal_open_files() but
71       takes an array of open file descriptors that must reference journal
72       files, instead of an array of file system paths. Pass the array of file
73       descriptors as second argument, and the number of array entries in the
74       third. The flags parameter must be passed as 0.
75
76       sd_journal objects cannot be used in the child after a fork. Functions
77       which take a journal object as an argument (sd_journal_next() and
78       others) will return -ECHILD after a fork.
79
80       sd_journal_close() will close the journal context allocated with
81       sd_journal_open() or sd_journal_open_directory() and free its
82       resources.
83
84       When opening the journal only journal files accessible to the calling
85       user will be opened. If journal files are not accessible to the caller,
86       this will be silently ignored.
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88       See sd_journal_next(3) for an example of how to iterate through the
89       journal after opening it with sd_journal_open().
90
91       A journal context object returned by sd_journal_open() references a
92       specific journal entry as current entry, similar to a file seek index
93       in a classic file system file, but without absolute positions. It may
94       be altered with sd_journal_next(3) and sd_journal_seek_head(3) and
95       related calls. The current entry position may be exported in cursor
96       strings, as accessible via sd_journal_get_cursor(3). Cursor strings may
97       be used to globally identify a specific journal entry in a stable way
98       and then later to seek to it (or if the specific entry is not available
99       locally, to its closest entry in time) sd_journal_seek_cursor(3).
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101       Notification of journal changes is available via sd_journal_get_fd()
102       and related calls.
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RETURN VALUE

105       The sd_journal_open(), sd_journal_open_directory(), and
106       sd_journal_open_files() calls return 0 on success or a negative
107       errno-style error code.  sd_journal_close() returns nothing.
108

NOTES

110       All functions listed here are thread-agnostic and only a single
111       specific thread may operate on a given object during its entire
112       lifetime. It's safe to allocate multiple independent objects and use
113       each from a specific thread in parallel. However, it's not safe to
114       allocate such an object in one thread, and operate or free it from any
115       other, even if locking is used to ensure these threads don't operate on
116       it at the very same time.
117
118       These APIs are implemented as a shared library, which can be compiled
119       and linked to with the libsystemd pkg-config(1) file.
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SEE ALSO

122       systemd(1), sd-journal(3), systemd-journald.service(8),
123       sd_journal_next(3), sd_journal_get_data(3)
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127systemd 243                                                 SD_JOURNAL_OPEN(3)
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