Provided by: libsystemd-dev_256.5-2ubuntu3_amd64 
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.
HISTORY
sd_journal_print(), sd_journal_printv(), sd_journal_send(), and sd_journal_sendv() were
added in version 187.
sd_journal_perror() was added in version 188.
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() were added in version 246.
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