1SD_JOURNAL_OPEN(3) sd_journal_open SD_JOURNAL_OPEN(3)
2
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
15 #include <systemd/sd-journal.h>
16 int sd_journal_open(sd_journal **ret, int flags);
18 int sd_journal_open_namespace(sd_journal **ret, const char *namespace,
20 int flags);
21 int sd_journal_open_directory(sd_journal **ret, const char *path,
23 int flags);
24 int sd_journal_open_directory_fd(sd_journal **ret, int fd, int flags);
26 int sd_journal_open_files(sd_journal **ret, const char **paths,
28 int flags);
29 int sd_journal_open_files_fd(sd_journal **ret, int fds[],
31 unsigned n_fds, int flags);
32 void sd_journal_close(sd_journal *j);
34
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 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).
62 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 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.
76 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.
85 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.
91 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 sd_journal_close() will close the journal context allocated with
97 sd_journal_open() or sd_journal_open_directory() and free its
98 resources.
99 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 See sd_journal_next(3) for an example of how to iterate through the
105 journal after opening it with sd_journal_open().
106 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).
116 Notification of journal changes is available via sd_journal_get_fd()
118 and related calls.
119
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
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.
133 These APIs are implemented as a shared library, which can be compiled
135 and linked to with the libsystemd pkg-config(1) file.
136
138 systemd(1), sd-journal(3), systemd-journald.service(8),
139 sd_journal_next(3), sd_journal_get_data(3)
140systemd 253 SD_JOURNAL_OPEN(3)