x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_JOURNAL_PRINT(3) sd_journal_print SD_JOURNAL_PRINT(3)
NAME
sd_journal_print, sd_journal_printv, sd_journal_send, sd_journal_sendv,
sd_journal_perror, SD_JOURNAL_SUPPRESS_LOCATION,
sd_journal_print_with_location, sd_journal_printv_with_location,
sd_journal_send_with_location, sd_journal_sendv_with_location,
sd_journal_perror_with_location - Submit log entries to the journal
SYNOPSIS
#include <systemd/sd-journal.h>
int sd_journal_print(int priority, const char *format, ...);
int sd_journal_printv(int priority, const char *format, va_list ap);
int sd_journal_send(const char *format, ...);
int sd_journal_sendv(const struct iovec *iov, int n);
int sd_journal_perror(const char *message);
int sd_journal_print_with_location(int priority, const char *file,
const char *line, const char *func,
const char *format, ...);
int sd_journal_printv_with_location(int priority, const char *file,
const char *line, const char *func,
const char *format, va_list ap);
int sd_journal_send_with_location(const char *file, const char *line,
const char *func, const char *format,
...);
int sd_journal_sendv_with_location(const char *file, const char *line,
const char *func,
const struct iovec *iov, int n);
int sd_journal_perror_with_location(const char *file, const char *line,
const char *func,
const char *message);
DESCRIPTION
sd_journal_print() may be used to submit simple, plain text log entries
to the system journal. The first argument is a priority value. This is
followed by a format string and its parameters, similar to printf(3) or
syslog(3). Note that currently the resulting message will be truncated
to LINE_MAX - 8. The priority value is one of LOG_EMERG, LOG_ALERT,
LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG, as
defined in syslog.h, see syslog(3) for details. It is recommended to
use this call to submit log messages in the application locale or
system locale and in UTF-8 format, but no such restrictions are
enforced. Note that log messages written using this function are
generally not expected to end in a new-line character. However, as all
trailing whitespace (including spaces, new-lines, tabulators and
carriage returns) are automatically stripped from the logged string, it
is acceptable to specify one (or more). Empty lines (after trailing
whitespace removal) are suppressed. On non-empty lines, leading
whitespace (as well as inner whitespace) is left unmodified.
sd_journal_printv() is similar to sd_journal_print() but takes a
variable argument list encapsulated in an object of type va_list (see
stdarg(3) for more information) instead of the format string. It is
otherwise equivalent in behavior.
sd_journal_send() may be used to submit structured log entries to the
system journal. It takes a series of format strings, each immediately
followed by their associated parameters, terminated by NULL. The
strings passed should be of the format "VARIABLE=value". The variable
name must be in uppercase and consist only of characters, numbers and
underscores, and may not begin with an underscore. (All assignments
that do not follow this syntax will be ignored.) The value can be of
any size and format. It is highly recommended to submit text strings
formatted in the UTF-8 character encoding only, and submit binary
fields only when formatting in UTF-8 strings is not sensible. A number
of well-known fields are defined, see systemd.journal-fields(7) for
details, but additional application defined fields may be used. A
variable may be assigned more than one value per entry. If this
function is used, trailing whitespace is automatically removed from
each formatted field.
sd_journal_sendv() is similar to sd_journal_send() but takes an array
of struct iovec (as defined in uio.h, see readv(3) for details) instead
of the format string. Each structure should reference one field of the
entry to submit. The second argument specifies the number of structures
in the array. sd_journal_sendv() is particularly useful to submit
binary objects to the journal where that is necessary. Note that this
function will not strip trailing whitespace of the passed fields, but
passes the specified data along unmodified. This is different from both
sd_journal_print() and sd_journal_send() described above, which are
based on format strings, and do strip trailing whitespace.
sd_journal_perror() is a similar to perror(3) and writes a message to
the journal that consists of the passed string, suffixed with ": " and
a human-readable representation of the current error code stored in
errno(3). If the message string is passed as NULL or empty string, only
the error string representation will be written, prefixed with nothing.
An additional journal field ERRNO= is included in the entry containing
the numeric error code formatted as decimal string. The log priority
used is LOG_ERR (3).
Note that sd_journal_send() is a wrapper around sd_journal_sendv() to
make it easier to use when only text strings shall be submitted. Also,
the following two calls are mostly equivalent:
sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid());
sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(),
"PRIORITY=%i", LOG_INFO,
NULL);
Note that these calls implicitly add fields for the source file,
function name and code line where invoked. This is implemented with
macros. If this is not desired, it can be turned off by defining
SD_JOURNAL_SUPPRESS_LOCATION before including sd-journal.h.
sd_journal_print_with_location(), sd_journal_printv_with_location(),
sd_journal_send_with_location(), sd_journal_sendv_with_location(), and
sd_journal_perror_with_location() are similar to their counterparts
without "_with_location", but accept additional parameters to
explicitly set the source file name, function, and line. The arguments
"file" and "line" must contain valid journal entries including the
variable name, e.g. "CODE_FILE=src/foo.c" and "CODE_LINE=666", while
"func" must only contain the function name, i.e. the value without
"CODE_FUNC=". These variants are primarily useful when writing custom
wrappers, for example in bindings for a different language.
syslog(3) and sd_journal_print() may largely be used interchangeably
functionality-wise. However, note that log messages logged via the
former take a different path to the journal server than the later, and
hence global chronological ordering between the two streams cannot be
guaranteed. Using sd_journal_print() has the benefit of logging source
code line, filenames, and functions as metadata along all entries, and
guaranteeing chronological ordering with structured log entries that
are generated via sd_journal_send(). Using syslog() has the benefit of
being more portable.
These functions implement a client to the Native Journal Protocol[1].
RETURN VALUE
The ten functions return 0 on success or a negative errno-style error
code. The errno(3) variable itself is not altered.
If systemd-journald(8) is not running (the socket is not present),
those functions do nothing, and also return 0.
THREAD SAFETY
All functions listed here are thread-safe and may be called in parallel
from multiple threads.
sd_journal_sendv() and sd_journal_sendv_with_location() are "async
signal safe" in the meaning of signal-safety(7).
sd_journal_print(), sd_journal_printv(), sd_journal_send(),
sd_journal_perror(), and their counterparts with "_with_location" are
not async signal safe.
NOTES
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
SEE ALSO
systemd(1), sd-journal(3), sd_journal_stream_fd(3), syslog(3),
perror(3), errno(3), systemd.journal-fields(7), signal(7), socket(7)
NOTES
1. Native Journal Protocol
https://systemd.io/JOURNAL_NATIVE_PROTOCOL
systemd 254 SD_JOURNAL_PRINT(3)
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