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,
8 sd_journal_print_with_location, sd_journal_printv_with_location,
9 sd_journal_send_with_location, sd_journal_sendv_with_location,
10 sd_journal_perror_with_location - Submit log entries to the journal
11
13 #include <systemd/sd-journal.h>
14 int sd_journal_print(int priority, const char *format, ...);
16 int sd_journal_printv(int priority, const char *format, va_list ap);
18 int sd_journal_send(const char *format, ...);
20 int sd_journal_sendv(const struct iovec *iov, int n);
22 int sd_journal_perror(const char *message);
24 int sd_journal_print_with_location(int priority, const char *file,
26 const char *line, const char *func,
27 const char *format, ...);
28 int sd_journal_printv_with_location(int priority, const char *file,
30 const char *line, const char *func,
31 const char *format, va_list ap);
32 int sd_journal_send_with_location(const char *file, const char *line,
34 const char *func, const char *format,
35 ...);
36 int sd_journal_sendv_with_location(const char *file, const char *line,
38 const char *func,
39 const struct iovec *iov, int n);
40 int sd_journal_perror_with_location(const char *file, const char *line,
42 const char *func,
43 const char *message);
44
46 sd_journal_print() may be used to submit simple, plain text log entries
47 to the system journal. The first argument is a priority value. This is
48 followed by a format string and its parameters, similar to printf(3) or
49 syslog(3). Note that currently the resulting message will be truncated
50 to LINE_MAX - 8. The priority value is one of LOG_EMERG, LOG_ALERT,
51 LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG, as
52 defined in syslog.h, see syslog(3) for details. It is recommended to
53 use this call to submit log messages in the application locale or
54 system locale and in UTF-8 format, but no such restrictions are
55 enforced. Note that log messages written using this function are
56 generally not expected to end in a new-line character. However, as all
57 trailing whitespace (including spaces, new-lines, tabulators and
58 carriage returns) are automatically stripped from the logged string, it
59 is acceptable to specify one (or more). Empty lines (after trailing
60 whitespace removal) are suppressed. On non-empty lines, leading
61 whitespace (as well as inner whitespace) is left unmodified.
62 sd_journal_printv() is similar to sd_journal_print() but takes a
64 variable argument list encapsulated in an object of type va_list (see
65 stdarg(3) for more information) instead of the format string. It is
66 otherwise equivalent in behavior.
67 sd_journal_send() may be used to submit structured log entries to the
69 system journal. It takes a series of format strings, each immediately
70 followed by their associated parameters, terminated by NULL. The
71 strings passed should be of the format "VARIABLE=value". The variable
72 name must be in uppercase and consist only of characters, numbers and
73 underscores, and may not begin with an underscore. (All assignments
74 that do not follow this syntax will be ignored.) The value can be of
75 any size and format. It is highly recommended to submit text strings
76 formatted in the UTF-8 character encoding only, and submit binary
77 fields only when formatting in UTF-8 strings is not sensible. A number
78 of well-known fields are defined, see systemd.journal-fields(7) for
79 details, but additional application defined fields may be used. A
80 variable may be assigned more than one value per entry. If this
81 function is used, trailing whitespace is automatically removed from
82 each formatted field.
83 sd_journal_sendv() is similar to sd_journal_send() but takes an array
85 of struct iovec (as defined in uio.h, see readv(3) for details) instead
86 of the format string. Each structure should reference one field of the
87 entry to submit. The second argument specifies the number of structures
88 in the array. sd_journal_sendv() is particularly useful to submit
89 binary objects to the journal where that is necessary. Note that this
90 function will not strip trailing whitespace of the passed fields, but
91 passes the specified data along unmodified. This is different from both
92 sd_journal_print() and sd_journal_send() described above, which are
93 based on format strings, and do strip trailing whitespace.
94 sd_journal_perror() is a similar to perror(3) and writes a message to
96 the journal that consists of the passed string, suffixed with ": " and
97 a human-readable representation of the current error code stored in
98 errno(3). If the message string is passed as NULL or empty string, only
99 the error string representation will be written, prefixed with nothing.
100 An additional journal field ERRNO= is included in the entry containing
101 the numeric error code formatted as decimal string. The log priority
102 used is LOG_ERR (3).
103 Note that sd_journal_send() is a wrapper around sd_journal_sendv() to
105 make it easier to use when only text strings shall be submitted. Also,
106 the following two calls are mostly equivalent:
107 sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
109 sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
111 "PRIORITY=%i", LOG_INFO,
112 NULL);
113 Note that these calls implicitly add fields for the source file,
115 function name and code line where invoked. This is implemented with
116 macros. If this is not desired, it can be turned off by defining
117 SD_JOURNAL_SUPPRESS_LOCATION before including sd-journal.h.
118 sd_journal_print_with_location(), sd_journal_printv_with_location(),
120 sd_journal_send_with_location(), sd_journal_sendv_with_location(), and
121 sd_journal_perror_with_location() are similar to their counterparts
122 without "_with_location", but accept additional parameters to
123 explicitly set the source file name, function, and line. The arguments
124 "file" and "line" must contain valid journal entries including the
125 variable name, e.g. "CODE_FILE=src/foo.c" and "CODE_LINE=666", while
126 "func" must only contain the function name, i.e. the value without
127 "CODE_FUNC=". These variants are primarily useful when writing custom
128 wrappers, for example in bindings for a different language.
129 syslog(3) and sd_journal_print() may largely be used interchangeably
131 functionality-wise. However, note that log messages logged via the
132 former take a different path to the journal server than the later, and
133 hence global chronological ordering between the two streams cannot be
134 guaranteed. Using sd_journal_print() has the benefit of logging source
135 code line, filenames, and functions as metadata along all entries, and
136 guaranteeing chronological ordering with structured log entries that
137 are generated via sd_journal_send(). Using syslog() has the benefit of
138 being more portable.
139 These functions implement a client to the Native Journal Protocol[1].
141
143 The ten functions return 0 on success or a negative errno-style error
144 code. The errno(3) variable itself is not altered.
145 If systemd-journald(8) is not running (the socket is not present),
147 those functions do nothing, and also return 0.
148
150 All functions listed here are thread-safe and may be called in parallel
151 from multiple threads.
152 sd_journal_sendv() and sd_journal_sendv_with_location() are "async
154 signal safe" in the meaning of signal-safety(7).
155 sd_journal_print(), sd_journal_printv(), sd_journal_send(),
157 sd_journal_perror(), and their counterparts with "_with_location" are
158 not async signal safe.
159
161 Functions described here are available as a shared library, which can
162 be compiled against and linked to with the libsystemd pkg-config(1)
163 file.
164 The code described here uses getenv(3), which is declared to be not
166 multi-thread-safe. This means that the code calling the functions
167 described here must not call setenv(3) from a parallel thread. It is
168 recommended to only do calls to setenv() from an early phase of the
169 program when no other threads have been started.
170
172 systemd(1), sd-journal(3), sd_journal_stream_fd(3), syslog(3),
173 perror(3), errno(3), systemd.journal-fields(7), signal(7), socket(7)
174
176 1. Native Journal Protocol
177 https://systemd.io/JOURNAL_NATIVE_PROTOCOL
178systemd 254 SD_JOURNAL_PRINT(3)