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