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. Note that log
32 messages written using this function are generally not expected to end
33 in a new-line character. However, as all trailing whitespace (including
34 spaces, new-lines, tabulators and carriage returns) are automatically
35 stripped from the logged string, it is acceptable to specify one (or
36 more). Empty lines (after trailing whitespace removal) are suppressed.
37 On non-empty lines, leading whitespace (as well as inner whitespace) is
38 left unmodified.
39 sd_journal_printv() is similar to sd_journal_print() but takes a
41 variable argument list encapsulated in an object of type va_list (see
42 stdarg(3) for more information) instead of the format string. It is
43 otherwise equivalent in behavior.
44 sd_journal_send() may be used to submit structured log entries to the
46 system journal. It takes a series of format strings, each immediately
47 followed by their associated parameters, terminated by NULL. The
48 strings passed should be of the format "VARIABLE=value". The variable
49 name must be in uppercase and consist only of characters, numbers and
50 underscores, and may not begin with an underscore. (All assignments
51 that do not follow this syntax will be ignored.) The value can be of
52 any size and format. It is highly recommended to submit text strings
53 formatted in the UTF-8 character encoding only, and submit binary
54 fields only when formatting in UTF-8 strings is not sensible. A number
55 of well-known fields are defined, see systemd.journal-fields(7) for
56 details, but additional application defined fields may be used. A
57 variable may be assigned more than one value per entry. If this
58 function is used, trailing whitespace is automatically removed from
59 each formatted field.
60 sd_journal_sendv() is similar to sd_journal_send() but takes an array
62 of struct iovec (as defined in uio.h, see readv(3) for details) instead
63 of the format string. Each structure should reference one field of the
64 entry to submit. The second argument specifies the number of structures
65 in the array. sd_journal_sendv() is particularly useful to submit
66 binary objects to the journal where that is necessary. Note that this
67 function will not strip trailing whitespace of the passed fields, but
68 passes the specified data along unmodified. This is different from both
69 sd_journal_print() and sd_journal_send() described above, which are
70 based on format strings, and do strip trailing whitespace.
71 sd_journal_perror() is a similar to perror(3) and writes a message to
73 the journal that consists of the passed string, suffixed with ": " and
74 a human-readable representation of the current error code stored in
75 errno(3). If the message string is passed as NULL or empty string, only
76 the error string representation will be written, prefixed with nothing.
77 An additional journal field ERRNO= is included in the entry containing
78 the numeric error code formatted as decimal string. The log priority
79 used is LOG_ERR (3).
80 Note that sd_journal_send() is a wrapper around sd_journal_sendv() to
82 make it easier to use when only text strings shall be submitted. Also,
83 the following two calls are mostly equivalent:
84 sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
86 sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
88 "PRIORITY=%i", LOG_INFO,
89 NULL);
90 Note that these calls implicitly add fields for the source file,
92 function name and code line where invoked. This is implemented with
93 macros. If this is not desired, it can be turned off by defining
94 SD_JOURNAL_SUPPRESS_LOCATION before including sd-journal.h.
95 syslog(3) and sd_journal_print() may largely be used interchangeably
97 functionality-wise. However, note that log messages logged via the
98 former take a different path to the journal server than the later, and
99 hence global chronological ordering between the two streams cannot be
100 guaranteed. Using sd_journal_print() has the benefit of logging source
101 code line, filenames, and functions as metadata along all entries, and
102 guaranteeing chronological ordering with structured log entries that
103 are generated via sd_journal_send(). Using syslog() has the benefit of
104 being more portable.
105
107 The five calls return 0 on success or a negative errno-style error
108 code. The errno(3) variable itself is not altered.
109 If systemd-journald(8) is not running (the socket is not present),
111 those functions do nothing, and also return 0.
112
114 All functions listed here are thread-safe and may be called in parallel
115 from multiple threads.
116 sd_journal_sendv() is "async signal safe" in the meaning of signal-
118 safety(7).
119 sd_journal_print, sd_journal_printv, sd_journal_send, and
121 sd_journal_perror are not async signal safe.
122
124 These APIs are implemented as a shared library, which can be compiled
125 and linked to with the libsystemd pkg-config(1) file.
126
128 systemd(1), sd-journal(3), sd_journal_stream_fd(3), syslog(3),
129 perror(3), errno(3), systemd.journal-fields(7), signal(7), socket(7)
130systemd 241 SD_JOURNAL_PRINT(3)