sd_journal_print(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | THREAD SAFETY | NOTES | HISTORY | SEE ALSO | NOTES | 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,
       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         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);

       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         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). 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         top

       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         top

       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         top

       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         top

       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         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)

NOTES         top

        1. Native Journal Protocol
           https://systemd.io/JOURNAL_NATIVE_PROTOCOL

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 2025-02-02.  (At that
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       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 258~devel                                     SD_JOURNAL_PRINT(3)

Pages that refer to this page: sd-journal(3)sd_journal_stream_fd(3)org.freedesktop.LogControl1(5)systemd.exec(5)file-hierarchy(7)systemd.directives(7)systemd.index(7)systemd.journal-fields(7)systemd-journald.service(8)