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 - 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);
DESCRIPTIONsd_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). 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.
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.
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.
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.
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.
RETURN VALUE
The four calls 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.
NOTES
The sd_journal_print(), sd_journal_printv(), sd_journal_send() and
sd_journal_sendv() interfaces are available as a shared library, which
can be compiled and linked to with the libsystemd-journal pkg-config(1)
file.
SEE ALSOsystemd(1), sd-journal(3), sd_journal_stream_fd(3), syslog(3),
perror(3), errno(3), systemd.journal-fields(7)systemd 208SD_JOURNAL_PRINT(3)