NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ASYNC SIGNAL SAFETY | NOTES | SEE ALSO | COLOPHON

SD_JOURNAL_PRINT(3)           sd_journal_print           SD_JOURNAL_PRINT(3)

NAME         top

       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         top

       #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);

DESCRIPTION         top

       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). 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 wil 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.

       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         top

       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.

ASYNC SIGNAL SAFETY         top

       sd_journal_sendv() is "async signal safe" in the meaning of
       signal(7).

       sd_journal_print, sd_journal_printv, sd_journal_send, and
       sd_journal_perror are not async signal safe.

NOTES         top

       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 pkg-config(1)
       file.

SEE ALSO         top

       systemd(1), sd-journal(3), sd_journal_stream_fd(3), syslog(3),
       perror(3), errno(3), systemd.journal-fields(7), signal(7), socket(7)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository 
       ⟨https://github.com/systemd/systemd.git⟩ on 2016-10-04.  If you dis‐
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       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 231                                              SD_JOURNAL_PRINT(3)