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_open_namespace, sd_journal_close,
9       sd_journal, SD_JOURNAL_LOCAL_ONLY, SD_JOURNAL_RUNTIME_ONLY,
10       SD_JOURNAL_SYSTEM, SD_JOURNAL_CURRENT_USER, SD_JOURNAL_OS_ROOT,
11       SD_JOURNAL_ALL_NAMESPACES, SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE - Open
12       the system journal for reading
13

SYNOPSIS

15       #include <systemd/sd-journal.h>
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17       int sd_journal_open(sd_journal **ret, int flags);
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19       int sd_journal_open_namespace(sd_journal **ret, const char *namespace,
20                                     int flags);
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22       int sd_journal_open_directory(sd_journal **ret, const char *path,
23                                     int flags);
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25       int sd_journal_open_directory_fd(sd_journal **ret, int fd, int flags);
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27       int sd_journal_open_files(sd_journal **ret, const char **paths,
28                                 int flags);
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30       int sd_journal_open_files_fd(sd_journal **ret, int fds[],
31                                    unsigned n_fds, int flags);
32
33       void sd_journal_close(sd_journal *j);
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DESCRIPTION

36       sd_journal_open() opens the log journal for reading. It will find all
37       journal files automatically and interleave them automatically when
38       reading. As first argument it takes a pointer to a sd_journal pointer,
39       which, on success, will contain a journal context object. The second
40       argument is a flags field, which may consist of the following flags
41       ORed together: SD_JOURNAL_LOCAL_ONLY makes sure only journal files
42       generated on the local machine will be opened.  SD_JOURNAL_RUNTIME_ONLY
43       makes sure only volatile journal files will be opened, excluding those
44       which are stored on persistent storage.  SD_JOURNAL_SYSTEM will cause
45       journal files of system services and the kernel (in opposition to user
46       session processes) to be opened.  SD_JOURNAL_CURRENT_USER will cause
47       journal files of the current user to be opened. If neither
48       SD_JOURNAL_SYSTEM nor SD_JOURNAL_CURRENT_USER are specified, all
49       journal file types will be opened.
50
51       sd_journal_open_namespace() is similar to sd_journal_open() but takes
52       an additional namespace parameter that specifies which journal
53       namespace to operate on. If specified as NULL the call is identical to
54       sd_journal_open(). If non-NULL only data from the namespace identified
55       by the specified parameter is accessed. This call understands two
56       additional flags: if SD_JOURNAL_ALL_NAMESPACES is specified the
57       namespace parameter is ignored and all defined namespaces are accessed
58       simultaneously; if SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE the specified
59       namespace and the default namespace are accessed but no others (this
60       flag has no effect when namespace is passed as NULL). For details about
61       journal namespaces see systemd-journald.service(8).
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63       sd_journal_open_directory() is similar to sd_journal_open() but takes
64       an absolute directory path as argument. All journal files in this
65       directory will be opened and interleaved automatically. This call also
66       takes a flags argument. The flags parameters accepted by this call are
67       SD_JOURNAL_OS_ROOT, SD_JOURNAL_SYSTEM, and SD_JOURNAL_CURRENT_USER. If
68       SD_JOURNAL_OS_ROOT is specified, journal files are searched for below
69       the usual /var/log/journal and /run/log/journal relative to the
70       specified path, instead of directly beneath it. The other two flags
71       limit which files are opened, the same as for sd_journal_open().
72
73       sd_journal_open_directory_fd() is similar to
74       sd_journal_open_directory(), but takes a file descriptor referencing a
75       directory in the file system instead of an absolute file system path.
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77       sd_journal_open_files() is similar to sd_journal_open() but takes a
78       NULL-terminated list of file paths to open. All files will be opened
79       and interleaved automatically. This call also takes a flags argument,
80       but it must be passed as 0 as no flags are currently understood for
81       this call. Please note that in the case of a live journal, this
82       function is only useful for debugging, because individual journal files
83       can be rotated at any moment, and the opening of specific files is
84       inherently racy.
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86       sd_journal_open_files_fd() is similar to sd_journal_open_files() but
87       takes an array of open file descriptors that must reference journal
88       files, instead of an array of file system paths. Pass the array of file
89       descriptors as second argument, and the number of array entries in the
90       third. The flags parameter must be passed as 0.
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92       sd_journal objects cannot be used in the child after a fork. Functions
93       which take a journal object as an argument (sd_journal_next() and
94       others) will return -ECHILD after a fork.
95
96       sd_journal_close() will close the journal context allocated with
97       sd_journal_open() or sd_journal_open_directory() and free its
98       resources.
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100       When opening the journal only journal files accessible to the calling
101       user will be opened. If journal files are not accessible to the caller,
102       this will be silently ignored.
103
104       See sd_journal_next(3) for an example of how to iterate through the
105       journal after opening it with sd_journal_open().
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107       A journal context object returned by sd_journal_open() references a
108       specific journal entry as current entry, similar to a file seek index
109       in a classic file system file, but without absolute positions. It may
110       be altered with sd_journal_next(3) and sd_journal_seek_head(3) and
111       related calls. The current entry position may be exported in cursor
112       strings, as accessible via sd_journal_get_cursor(3). Cursor strings may
113       be used to globally identify a specific journal entry in a stable way
114       and then later to seek to it (or if the specific entry is not available
115       locally, to its closest entry in time) sd_journal_seek_cursor(3).
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117       Notification of journal changes is available via sd_journal_get_fd()
118       and related calls.
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RETURN VALUE

121       The sd_journal_open(), sd_journal_open_directory(), and
122       sd_journal_open_files() calls return 0 on success or a negative
123       errno-style error code.  sd_journal_close() returns nothing.
124

NOTES

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

138       systemd(1), sd-journal(3), systemd-journald.service(8),
139       sd_journal_next(3), sd_journal_get_data(3)
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143systemd 251                                                 SD_JOURNAL_OPEN(3)
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