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27 .Nd Apple System Log utility
62 .Fl x Ar file Ar expression
65 .Fl c Ar process Op mask
75 is a command-line utility for a variety of tasks relating to the Apple System Log (ASL) facility.
76 It provides mechanisms for sending and viewing log messages,
77 copying log messages to ASL format data store files,
78 and for controlling the flow of log messages from client processes.
84 prints a usage message.
88 option is used send log messages to the
91 either locally or to a remote server if the
95 There are two main forms of the command.
98 option is used, then it must be followed by a list of keys and values.
99 A structured message will be sent to the server with the keys and values given as arguments.
100 If a key or a value has embedded white space, it must be enclosed in quotes.
102 Note that the text of the log message should be supplied as a value following the
108 option is not specified, then the rest of the command line is treated as the message text.
109 The text may be preceded by
111 to set the log level (priority) of the message.
112 Levels may be an integer value corresponding the the log levels specified in
116 or they may be a string.
117 String values are case insensitive, and should be one of:
145 option is omitted, the log level defaults to 7 (Debug).
148 only requires one or two leading characters for a level specification.
149 A single character suffices in most cases.
154 for Panic / Emergency, and
162 daemon filters and saves log messages to different output streams.
163 One module saves messages to files specified in the
166 Those log files may be examined with any file printing or editing utility,
169 .Dl cat /var/log/system.log
171 Another module saves messages in a data store (/var/log/asl).
173 If invoked with no arguments,
175 fetches all messages from the active data store.
176 Messages are then printed to standard output,
177 subject to formatting options and character encoding as described below.
178 Some log messages are read-access controlled,
179 so only messages that are readable by the user running
181 will be fetched and printed.
187 fetches and prints console messages.
190 option is actually an alias for the expression:
192 .Dl -k Facility com.apple.console
194 See the EXPRESSIONS section below for more details.
196 Individual ASL data store files may be read by providing one or more file names as arguments to the
199 This may be useful when searching archived files, files on alternate disk volumes,
200 or files created as export files with the
206 option may be followed by a list of directory paths.
208 will read or search all ASL data store files in those directories.
209 Any files that are not readable will be skipped.
214 will open all readable files in the default ASL archive directory /var/log/asl.archive.
219 will open all readable files in the ASL store directory /var/log/asl.
221 Legacy ASL database files that were written by
223 on Mac OS X 10.5 (Leopard) may also be read using the
226 However only one such legacy database may be read or searched at a time.
227 Note that a legacy database may be read and copied into a new ASL data store format file using a combination of
237 to start processing messages beginning at the time of the last system startup.
238 If used in conjunction with
240 all messages since the last system startup are displayed, or matched against an expression, before
242 waits for new messages.
248 to wait for new messages.
251 prints the last 10 messages,
252 then waits for new messages to be added to the data store.
253 A number following the
255 option specifies the number of messages to print and overrides the default value of 10.
262 to view all messages in the data store before watching for new messages.
265 will display messages since the last system startup before watching for new messages.
268 is equivalent to using
278 option is similar to watching a log file using, e.g.
280 .Dl tail -f /var/log/system.log
284 option can only be used when reading the system's ASL data store or when reading a single data store file,
285 and when printing messages to standard output.
289 option is specified, messages are copied to the named file rather than being printed.
290 The file will be created if it does not exist.
292 When called without the
294 option, messages are printed to standard output.
295 Messages are printed in a format similar to that used in the system.log file,
296 except that the message priority level is printed between angle-brackets.
298 The output format may by changed by specifying the
301 Non-printable and control characters are encoded by default.
302 Text encoding may be controlled using the
307 may be one of the following:
309 .Bl -tag -width "xxxx"
313 daemon for system log files, e.g. /var/log/system.log.
315 Standard (default) format.
318 but includes the message priority level.
320 Prints the complete message structure.
321 Each key/value pair is enclosed in square brackets.
322 Embedded closing brackets and white space are escaped.
323 Time stamps are printed as seconds since the epoch by default, but may also be
324 printed in local time or UTC if the
326 option is specified (see below).
328 The list of messages is printed as an XML property list.
329 Each message is represented as a dictionary in a array.
330 Dictionary keys represent message keys.
331 Dictionary values are strings.
334 Each of the format styles above may optionally be followed by a dot character and an integer value, for example:
338 This causes sub-second time values to be printed.
339 In the example above, 4 decimal digits would be printed.
340 The sub-second time values come from the value of the TimeNanoSec key in the ASL message.
341 If the TimeNanoSec key is missing, a value of zero is used.
345 argument may also be a custom print format string.
346 A custom format should in most cases be enclosed in single quotes to prevent the shell from substituting
347 special characters and breaking at white space.
349 Custom format strings may include variables of the form
353 .Dq $((Name)(format)) .
354 which will be expanded to the value associated with the named key.
355 For example, the command:
357 .Dl syslog -F '$Time $Host $(Sender)[$(PID)] <$((Level)(str))>: $Message'
359 produces output similar to the
364 form is sufficient in most cases.
365 However, the second form:
367 must be used if the name is not delimited by white space.
368 The third form allows different formats of the value to be printed.
369 For example, a message priority level may appear as an integer value (e.g.
371 or as a string (``Error'').
372 The following print formats are known.
374 .Bl -tag -width "$((Time)([+|-]HH[:MM]))"
376 Formats a Level value as a string, for example
381 Note that $(Level) or $Level formats the value as an integer 0 through 7.
383 Formats a Time value as the number of seconds since the Epoch.
385 Alias for $((Time)(sec)).
387 Formats a Time value as a string of the form
388 .Dq "Mmm dd hh:mm:ss" ,
389 where Mmm is the abbreviation for the month, dd is the date (1 - 31) and hh:mm:ss is the time.
390 The local timezone is used.
392 Alias for $((Time)(local)).
394 Formats a Time value as a string of the form
395 .Dq "yyyy-mm-dd hh:mm:ssZ" ,
396 using Coordinated Universal Time, or the
400 Alias for $((Time)(utc)).
402 Where X may be any letter in the range A - Z or a - z.
403 Formats the Time using the format
404 .Dq "yyyy-mm-dd hh:mm:ssX" ,
405 using the specified nautical timezone.
406 Z is the same as UTC/Zulu time. Timezones A - M (except J) decrease by one hour to the east of the
408 Timezones N - Y increase by one hour to the west of Z.
409 M and Y have the same clock time, but differ by one day.
410 J is used to indicate the local timezone.
411 When printing using $((Time)(J)), the output format is
412 .Dq "yyyy-mm-dd hh:mm:ss" ,
413 without a trailing timezone letter.
415 Specifies the local timezone.
416 The timezone offset from UTC follows the date and time.
417 The time is formatted as
418 .Dq "yyyy-mm-dd hh:mm:ss[+|-]HH[:MM]" .
419 Minutes in the timezone offset are only printed if they are non-zero.
420 .It $((Time)(ISO8601))
421 Specifies the local timezone and ISO 8601 extended format.
422 The timezone offset from UTC follows the date and time.
423 The time is formatted as
424 .Dq "yyyy-mm-ddThh:mm:ss[+|-]HH[:MM]" .
425 Minutes in the timezone offset are only printed if they are non-zero.
426 Note that this differs from
428 format only in that a
430 character separates the date and time.
431 .It $((Time)(ISO8601B))
432 Specifies the local timezone and ISO 8601 basic format, in the form:
433 .Dq "yyyymmddThhmmss[+|-]HH[:MM]" .
434 .It $((Time)(ISO8601Z))
435 Specifies UTC/Zulu time and ISO 8601 extended format, in the form:
436 .Dq "yyyy-mm-ddThh:mm:ssZ" .
437 .It $((Time)(ISO8601BZ))
438 Specifies UTC/Zulu time and ISO 8601 basic format, in the form:
439 .Dq "yyyymmddThhmmssZ" .
440 .It $((Time)([+|-]HH[:MM]))
441 Specifies an offset (+ or -) of the indicated number of hours (HH) and optionally minutes (MM) to UTC.
442 The value is formatted as a string of the form
443 .Dq "yyyy-mm-dd hh:mm:ss[+|-]HH[:MM]" .
444 Minutes in the timezone offset are only printed if they are non-zero.
447 Each of the print formats listed above for Time values may optionally be followed by a dot character and an integer value.
448 In that case, sub-second time values will be printed.
449 For example, the following line prints messages with a UTC time format, and includes 6 digits of sub-second time:
451 .Dl syslog -F '$((Time)(utc.6)) $Host $(Sender)[$(PID)] <$((Level)(str))>: $Message
453 If a custom format is not being used to specify the format for Time values, then Time values
454 are generally converted to local time, except when the
456 option is used, in which case times are printed as the number of seconds since the epoch.
459 option may be used to control the format used for timestamps.
462 may be one of the following:
464 .Bl -tag -width "local or lcl"
466 Times are printed as the number of seconds since the epoch.
468 Times are converted to the local time zone, and printed with the format
470 where mmm is the month name abbreviated as three characters.
472 Times are converted to UTC, and printed with the format
473 .Dl yyyy-mm-dd hh:mm:ssZ
475 Times are converted to the indicated nautical time zone,
476 printed in the same format as UTC.
478 is interpreted as the local timezone and printed in the same format,
479 but without a trailing timezone letter.
481 is interpreted as the local timezone and printed with the format
482 .Dl yyyy-mm-dd hh:mm:ss[+|-]HH[:MM] .
485 string represents the local timezone offset from UTC in hours,
486 or in hours and minutes if minutes are non-zero.
488 Times are printed with the format specified by ISO 8601:
489 .Dl yyyy-mm-ddThh:mm:ss[+|-]HH[:MM] .
490 This is the same as the
493 .Dq T character separates the date and time components.
495 The specified offset is used to adjust time.
498 Each of the time formats above may optionally be followed by a dot character and an integer value.
499 In that case, sub-second time values will be printed.
506 option is a short form for
509 By default, control characters and non-printable characters are encoded in the output stream.
510 In some cases this may make messages less natural in appearance.
511 The encoding is designed to preserve all the information in the log message,
512 and to prevent malicious users from spoofing or obscuring information in log messages.
519 formats is encoded as it is by the
524 Newlines and tabs are also encoded as "\\n" and "\\t" respectively.
527 format, space characters embedded in log message keys are encoded as "\\s"
528 and embedded brackets are escaped to print as "\\[" and "\\]".
530 XML format output requires that keys are valid UTF8 strings.
531 Keys which are not valid UTF8 are ignored, and the associated value is not printed.
533 Values that contain legal UTF8 are printed as strings.
534 Ampersand, less than, greater than, quotation mark, and apostrophe characters are encoded according to XML conventions.
535 Embedded control characters are encoded as
537 where NN is the character's hexadecimal value.
539 Values that do not contain legal UTF8 are encoded in base-64 and printed as data objects.
543 option may be used to explicitly control the text encoding.
546 may be one of the following:
548 .Bl -tag -width "safe"
550 This is the default encoding for
553 Encodes backspace characters as ^H.
554 Carriage returns are mapped to newlines.
555 A tab character is appended after newlines so that message text is indented.
557 The C-style backslash encoding similar to that produced by the
559 command, as described above.
566 encoding is to prevent obvious message spoofing or damage.
567 The appearance of messages printed will depend on terminal settings and UTF-8 string handling.
568 It is possible that messages printed using the
572 options may be garbled or subject to manipulation through the use of control characters and control sequences
573 embedded in user-supplied message text.
576 encoding should be used to view messages if there is any suspicion
577 that message text may have been used to manipulate the printed representation.
579 If no further command line options are specified,
581 displays all messages, or copies all messages to a data store file.
582 However, an expression may be specified using the
588 Expressions specify matching criteria.
589 They may be used to search for messages of interest.
594 .Dl -k key [[op] val]
598 option may be followed by one, two, or three arguments.
599 A single argument causes a match to occur if a message has the specified key, regardless of value.
600 If two arguments are specified, a match occurs when a message has exactly the specified value for a given key.
601 For example, to find all messages sent by the portmap process:
603 .Dl syslog -k Sender portmap
607 option is treated as an alias for the expression:
609 .Dl -k Facility com.apple.console
611 This provides a quick way to search for console messages.
613 If three arguments are given, they are of the form
614 .Fl k Ar key operation value .
616 supports the following matching operators:
618 .Bl -tag -width "xxx" -compact
626 greater than or equal to
630 less than or equal to
633 Additionally, the operator may be preceded by one or more of the following modifiers:
635 .Bl -tag -width "xxx" -compact
639 regular expression (see
651 More complex search expressions may be built by combining two or more simple expressions.
652 A complex expression that has more than one
653 .Dq -k key [[op] val]
654 term matches a message if all of the key-value operations match.
655 Logically, the result is an AND of all of key-value operations.
658 .Dl syslog -k Sender portmap -k Time ge -2h
660 finds all messages sent by portmap in the last 2 hours
661 (-2h means "two hours ago").
665 option may be used to build even more complex searches by providing an OR operation.
666 If two or more sub-expressions are given, separated by
668 options, then a match occurs is a message matches any of the sub-expressions.
669 For example, to find all messages which have either a
673 or that have a numeric priority level of 4 or less:
675 .Dl syslog -k Sender portmap -o -k Level Nle 4
677 Log priority levels are internally handled as an integer value between 0 and 7.
678 Level values in expressions may either be given as integers, or as string equivalents.
679 See the table string values in the SENDING MESSAGES section for details.
680 The example query above could also be specified with the command:
682 .Dl syslog -k Sender portmap -o -k Level Nle warning
685 A special convention exists for matching time stamps.
686 An unsigned integer value is regarded as the given number of seconds since
687 0 hours, 0 minutes, 0 seconds, January 1, 1970, Coordinated Universal Time.
688 An negative integer value is regarded as the given number of seconds before the current time.
689 For example, to find all messages of Error priority level (3) or less which were logged in the last 30 seconds:
691 .Dl syslog -k Level Nle error -k Time ge -30
693 a relative time value may be optionally followed by one of the characters
700 to specify seconds, minutes, hours, days, or weeks respectively.
701 Upper case may be used equivalently.
702 A week is taken to be 7 complete days (i.e. 604800 seconds).
703 .Ss FILTERING CONTROLS
704 Clients of the Apple System Log facility using either the
708 interfaces may specify a log filter mask.
709 The mask specifies which messages should be sent to the
711 daemon by specifying a yes/no setting for each priority level.
712 Many clients set a filter mask to avoid sending relatively unimportant messages.
713 Debug or Info priority level messages are generally only useful for debugging operations.
714 By setting a filter mask, a process can improve performance by avoiding spending
715 time sending messages that are in most cases unnecessary.
719 option may be used to control filtering.
720 In addition to the internal filter mask value that processes may set as described above,
721 the system maintains a global
724 This filter is normally
726 meaning that it has no effect.
727 If a value is set for the master filter mask, it overrides the local filter mask for all processes.
728 Root user access is required to set the master filter mask value.
730 The current setting of the master filter mask may be inspected using:
734 The value of the master filter mask my be set by providing a second argument following
736 The value may a set of characters from the set
738 These correspond to the priority levels Emergency (Panic), Alert, Critical, Error, Warning, Notice, Info, and Debug.
741 may be used for Error, as it is used for sending messages.
742 The master filter mask may be deactivated with:
746 Since it is common to use the filter mask as a
748 mechanism, for example to cut off messages with Debug and Info priority,
749 a single character from the list above may be specified, preceded by a minus sign.
752 uses a filter mask starting at level 0 (Emergency)
755 For example, to set the master filter mask to cause all processes to log messages from Emergency up to Debug:
759 While the master filter mask may be set to control the messages produced by all processes,
760 another filter mask may be specified for an individual process.
761 If a per-process filter mask is set, it overrides both the local filter mask and the master filter mask.
762 The current setting for a per-process filter mask may be inspected using
766 is either a PID or the name of a process.
767 If a name is used, it must uniquely identify a process.
768 To set a per-process filter mask, an second argument may be supplied following
770 as described above for the master filter mask.
771 Root access is required to set the per-process filter mask for system (UID 0) processes.
775 server follows filtering rules specified in the /etc/asl.conf file.
776 When the remote-control mechanism is used to change the filter of a process,
778 will save any messages received from that process until the remote-control filter is turned off.
779 .Ss SERVER CONFIGURATION
782 starts up, and when it receives a HUP signal, it re-reads its configuration settings from /etc/asl.conf.
783 It is sometimes useful to change configuration parameters temporarily, without needing to make changes
784 to the configuration file.
785 Any of the configuration options that may be set in the file (following an ``='' character) may also
786 be sent to syslogd using the
788 flag (without an ``='' character).
789 For example, to temporarily disable the kernel message-per-second limit:
791 .Dl syslog -config mps_limit 0
793 Note that only the superuser (root) may change configuration parameters.
795 In addition to the parameter setting options that are described in the
797 manual page, an additional option:
799 .Dl syslog -config reset
803 to reset its configuration.
804 .Ss ASL OUTPUT MODULES
805 ASL Output Modules are named configuration bundles used by the ASL server
807 and by the ASL filesystem manager
809 The /etc/asl.conf file represents the system's primary output module,
810 and is given the name
812 Other modules are read from files in the /etc/asl directory.
813 File names serve as module names.
814 ASL Output Modules are described in detail in
820 prints a summary of all loaded ASL Output Modules.
821 The summary includes the output files and ASL store directories used by each module,
822 a list of the module's configuration rules, and the module's current enabled or disabled status.
824 prints a summary for the module with the given name.
826 ASL Output Modules may be enabled or disabled using the command:
833 Note that only the superuser (root) may enable or disable a module.
836 (including the single-quote characters)
837 may be used to change the status of all ASL Output Modules,
838 excluding the primary com.apple.asl module.
839 com.apple.asl may be enabled or disabled, but only specifically by name.
841 If a module includes rotated files, the command:
848 Will force the module to checkpoint all of its rotated files,
849 or just the single optionally named file.
851 (including the single-quote characters)
852 may be used to force checkpointing of all rotated files for all ASL Output Modules,
853 including the primary com.apple.asl module.
855 Note that only the superuser (root) may force files to be checkpointed.
857 The checkpoint action sends a command to
859 and waits for a reply to be returned.
860 This means that any files currently in use will be checkpointed when the
872 utility appeared in Mac OS X 10.4.
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