95 lines
3.1 KiB
ReStructuredText
95 lines
3.1 KiB
ReStructuredText
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=======
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Logging
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=======
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NuttX provides the SYSLOG for application and OS logging, which can be
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configured in various ways to select how these messages are displayed
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(see details :doc:`here </components/drivers/special/syslog>`).
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Applications can emit logging messages using the standard :c:func:`syslog`
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interface.
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.. note:: The standard :c:func:`openlog` and :c:func:`closelog`
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are not currently supported.
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.. c:function:: void syslog(int priority, const char *fmt, ...)
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This interface allows to send messages to SYSLOG using standard
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:c:func:`printf` formatting.
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Each message sent to SYSLOG is assigned a priority. Depending
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on system configuration this message may or not appear in the
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output.
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:param priority: A priority given by ``LOG_*`` family of
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definitions.
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:param fmt: The format string
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.. c:function:: void vsyslog(int priority, const char *fmt, va_list ap)
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Performs the same task as :c:func:`syslog` with the
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difference that it takes a set of arguments which have been obtained
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using the :file:`include/stdarg.h` variable argument list macros.
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.. c:function:: int setlogmask(int mask)
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Sets the logging mask which controls which messages appear on SYSLOG
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output. :c:func:`setlogmask` is not a thread-safe, re-entrant function.
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Concurrent use will have undefined behavior.
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:param mask: The new mask to set.
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See :c:macro:`LOG_MASK` and :c:macro:`LOG_UPTO`.
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Per OpenGroup.org "If the maskpri argument is 0, the current log mask
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is not modified." In this implementation, the value zero is permitted
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in order to disable all syslog levels.
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:returns: The previous mask.
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.. warning:: Per POSIX the syslog mask should be a per-process value but in
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NuttX, the scope of the mask is dependent on the nature of the build:
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* Flat Build: There is one, global SYSLOG mask that controls all output.
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* Protected Build: There are two SYSLOG masks. One within the kernel
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that controls only kernel output. And one in user-space that controls
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only user SYSLOG output.
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* Kernel Build: The kernel build is compliant with the POSIX requirement:
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There will be one mask for each user process, controlling the SYSLOG
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output only form that process. There will be a separate mask
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accessible only in the kernel code to control kernel SYSLOG output.
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Priority Levels
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===============
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The following levels are defined:
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================ ===========
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Priority (macro) Description
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================ ===========
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``LOG_EMERG`` System is unusable
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``LOG_ALERT`` Action must be taken immediately
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``LOG_CRIT`` Critical conditions
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``LOG_ERR`` Error conditions
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``LOG_WARNING`` Warning conditions
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``LOG_NOTICE`` Normal, but significant, condition
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``LOG_INFO`` Informational message
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``LOG_DEBUG`` Debug-level message
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================ ===========
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Priority mask
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=============
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The following macros can be used with :c:func:`setlogmask`:
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.. c:macro:: LOG_MASK(p)
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Returns the logmask corresponding priority ``p``
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.. c:macro:: LOG_UPTO(p)
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Returns the logmask of all SYSLOG priorities
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up to and including ``p``.
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.. c:macro:: LOG_ALL
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Mask corresponding to all priorities enabled
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