1SD_JOURNAL_PRINT(3) sd_journal_print SD_JOURNAL_PRINT(3)
2
6 sd_journal_print, sd_journal_printv, sd_journal_send, sd_journal_sendv,
7 sd_journal_perror, SD_JOURNAL_SUPPRESS_LOCATION - Submit log entries to
8 the journal
9
11 #include <systemd/sd-journal.h>
12 int sd_journal_print(int priority, const char *format, ...);
14 int sd_journal_printv(int priority, const char *format, va_list ap);
16 int sd_journal_send(const char *format, ...);
18 int sd_journal_sendv(const struct iovec *iov, int n);
20 int sd_journal_perror(const char *message);
22
24 sd_journal_print() may be used to submit simple, plain text log entries
25 to the system journal. The first argument is a priority value. This is
26 followed by a format string and its parameters, similar to printf(3) or
27 syslog(3). The priority value is one of LOG_EMERG, LOG_ALERT, LOG_CRIT,
28 LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG, as defined in
29 syslog.h, see syslog(3) for details. It is recommended to use this call
30 to submit log messages in the application locale or system locale and
31 in UTF-8 format, but no such restrictions are enforced.
32 sd_journal_printv() is similar to sd_journal_print() but takes a
34 variable argument list encapsulated in an object of type va_list (see
35 stdarg(3) for more information) instead of the format string. It is
36 otherwise equivalent in behavior.
37 sd_journal_send() may be used to submit structured log entries to the
39 system journal. It takes a series of format strings, each immediately
40 followed by their associated parameters, terminated by NULL. The
41 strings passed should be of the format "VARIABLE=value". The variable
42 name must be in uppercase and consist only of characters, numbers and
43 underscores, and may not begin with an underscore. (All assignments
44 that do not follow this syntax will be ignored.) The value can be of
45 any size and format. It is highly recommended to submit text strings
46 formatted in the UTF-8 character encoding only, and submit binary
47 fields only when formatting in UTF-8 strings is not sensible. A number
48 of well known fields are defined, see systemd.journal-fields(7) for
49 details, but additional application defined fields may be used. A
50 variable may be assigned more than one value per entry.
51 sd_journal_sendv() is similar to sd_journal_send() but takes an array
53 of struct iovec (as defined in uio.h, see readv(3) for details) instead
54 of the format string. Each structure should reference one field of the
55 entry to submit. The second argument specifies the number of structures
56 in the array. sd_journal_sendv() is particularly useful to submit
57 binary objects to the journal where that is necessary.
58 sd_journal_perror() is a similar to perror(3) and writes a message to
60 the journal that consists of the passed string, suffixed with ": " and
61 a human readable representation of the current error code stored in
62 errno(3). If the message string is passed as NULL or empty string, only
63 the error string representation will be written, prefixed with nothing.
64 An additional journal field ERRNO= is included in the entry containing
65 the numeric error code formatted as decimal string. The log priority
66 used is LOG_ERR (3).
67 Note that sd_journal_send() is a wrapper around sd_journal_sendv() to
69 make it easier to use when only text strings shall be submitted. Also,
70 the following two calls are mostly equivalent:
71 sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
73 sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
75 "PRIORITY=%i", LOG_INFO,
76 NULL);
77 Note that these calls implicitly add fields for the source file,
79 function name and code line where invoked. This is implemented with
80 macros. If this is not desired, it can be turned off by defining
81 SD_JOURNAL_SUPPRESS_LOCATION before including sd-journal.h.
82 syslog(3) and sd_journal_print() may largely be used interchangeably
84 functionality-wise. However, note that log messages logged via the
85 former take a different path to the journal server than the later, and
86 hence global chronological ordering between the two streams cannot be
87 guaranteed. Using sd_journal_print() has the benefit of logging source
88 code line, filenames, and functions as metadata along all entries, and
89 guaranteeing chronological ordering with structured log entries that
90 are generated via sd_journal_send(). Using syslog() has the benefit of
91 being more portable.
92
94 The four calls return 0 on success or a negative errno-style error
95 code. The errno(3) variable itself is not altered.
96 If systemd-journald(8) is not running (the socket is not present),
98 those functions do nothing, and also return 0.
99
101 sd_journal_sendv() is "async signal safe" in the meaning of signal(7).
102 sd_journal_print, sd_journal_printv, sd_journal_send, and
104 sd_journal_perror are not async signal safe.
105
107 The sd_journal_print(), sd_journal_printv(), sd_journal_send() and
108 sd_journal_sendv() interfaces are available as a shared library, which
109 can be compiled and linked to with the libsystemd pkg-config(1) file.
110
112 systemd(1), sd-journal(3), sd_journal_stream_fd(3), syslog(3),
113 perror(3), errno(3), systemd.journal-fields(7), signal(7), socket(7)
114systemd 219 SD_JOURNAL_PRINT(3)