systemd Developer Lennart Poettering lennart@poettering.net sd_journal_print 3 sd_journal_print sd_journal_printv sd_journal_send sd_journal_sendv Submit log entries to the journal #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 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 printf3 or syslog3. 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 syslog3 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 stdarg3 for more information) instead of the format string. It is otherwise equivalent in behaviour. 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 a 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. 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-fields7 for details, but additional application defined fields may be used. sd_journal_sendv() is similar to sd_journal_send() but takes an array of struct iovec (as defined in uio.h, see readv3 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 sd_journal_send() is a wapper 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. syslog3 and and sd_journal_print() may mostly be used interchangably 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, file names, and functions as meta data 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. The four calls return 0 on success or a negative errno-style error code. The sd_journal_print(), sd_journal_printv(), sd_journal_send() and sd_journal_sendv() interfaces are available as shared library, which can be compiled and linked to with the libsystemd-journal pkg-config1 file. systemd1, sd-journal3, sd_journal_stream_fd3, syslog3, systemd.journal-fields7