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Timothy Stack 4ccae48aea [bookmarks] add support for tags and comments for log lines 
Initial work for #446 and #447
  TODO: filtering on tags/comments

Also did a bunch of clang-tidy cleanups and improvements to
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2018-05-17 07:06:50 -07:00

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lnav - A fancy log file viewer
DESCRIPTION
===========
The log file navigator, lnav, is an enhanced log file viewer that
takes advantage of any semantic information that can be gleaned from
the files being viewed, such as timestamps and log levels. Using this
extra semantic information, lnav can do things like interleaving
messages from different files, generate histograms of messages over
time, and providing hotkeys for navigating through the file. It is
hoped that these features will allow the user to quickly and
efficiently zero in on problems.
OPENING PATHS/URLs
==================
The main arguments to lnav are the files, directories, glob patterns,
or URLs to be viewed. If no arguments are given, the default syslog
file for your system will be opened. These arguments will be polled
periodically so that any new data or files will be automatically
loaded. If a previously loaded file is removed or replaced, it will
be closed and the replacement opened.
Note: When opening SFTP URLs, if the password is not provided for the
host, the SSH agent can be used to do authentication.
OPTIONS
=======
Lnav takes a list of files to view and/or you can use the flag
arguments to load well-known log files, such as the syslog or apache
log files. The flag arguments are:
-a Load all of the most recent log file types.
-r Load older rotated log files as well.
When using the flag arguments, lnav will look for the files relative
to the current directory and its parent directories. In other words,
if you are working within a directory that has the well-known log
files, those will be preferred over any others.
Any files given on the command-line are scanned to determine their log
file format and to create an index for each line in the file. You do
not have to manually specify the log file format. The currently
supported formats are: syslog, apache, strace, tcsh history, and
generic log files with timestamps.
Lnav will also display data piped in on the standard input. The
following options are available when doing so:
-t Prepend timestamps to the lines of data being read in
on the standard input.
-w file Write the contents of the standard input to this file.
To automatically execute queries or lnav commands after the files
have been loaded, you can use the following options:
-c cmd A command, query, or file to execute. The first character
determines the type of operation: a colon is used for the
built-in commands; a semi-colon for SQL queries; and a
pipe symbol (|) for executing a file containing other
commands. For example, to open the file "foo.log" and go
to the tenth line in the file, you can do:
lnav -c ':goto 10' foo.log
This option can be given multiple times to execute multiple
operations in sequence.
-f file A file that contains commands, queries, or files to execute.
This option is a shortcut for "-c '|file'". You can use a
dash (-) to execute commands from the standard input.
To execute commands/queries without the opening the interactive text UI,
you can pass the '-n' option. This combination of options allows you to
write scripts for processing logs with lnav. For example, to get a list
of IP addresses that dhclient has bound to in CSV format:
#! /usr/bin/lnav -nf
# Usage: dhcp_ip.lnav /var/log/messages
# Only include lines that look like:
# Apr 29 00:31:56 example-centos5 dhclient: bound to 10.1.10.103 -- renewal in 9938 seconds.
:filter-in dhclient: bound to
# The log message parser will extract the IP address as col_0, so we
# select that and alias it to "dhcp_ip".
;select distinct col_0 as dhcp_ip from logline;
# Finally, write the results of the query to stdout.
:write-csv-to -
DISPLAY
=======
The main part of the display shows the log lines from the files interleaved
based on time-of-day. New lines are automatically loaded as they are appended
to the files and, if you are viewing the bottom of the files, lnav will scroll
down to display the new lines, much like 'tail -f'.
On color displays, the lines will be highlighted as follows:
* Errors will be colored in ${ansi_red}red${ansi_norm};
* warnings will be ${ansi_yellow}yellow${ansi_norm};
* boundaries between days will be ${ansi_underline}underlined${ansi_norm}; and
* various color highlights will be applied to: IP addresses, SQL keywords,
XML tags, file and line numbers in Java backtraces, and quoted strings.
To give you an idea of where you are spatially, the right side of the
display has a proportionally sized 'scroll bar' that indicates your
current position in the files. The scroll bar will also show areas of
the file where warnings or errors are detected by coloring the bar
yellow or red, respectively. Tick marks will also be added to the
left and right hand side of the bar, for search hits and bookmarks.
A bar on the left side is color coded and broken up to indicate which
messages are from the same file. Pressing the left-arrow or 'h' will
reveal the source file names for each message and pressing again will
show the full paths.
When at the bottom of the log view, a summary line will be displayed on the
right-hand-side to give you some more information about your logs, including:
how long ago the last message was generated, the number of log files, the
error rate, and how much time the logs cover. The error rate display shows
the errors-per-minute over the last five minutes. A bar chart is also
overlaid on the "Error rate" label to show the error rate over the past ten
seconds. For example, if there have not been many errors in the past five
minutes and there is a sudden spike, the bar chart will fill up completely.
But, if there has been a steady stream of errors, then the chart will only
partially fill based on the recent error frequency.
Above and below the main body are status lines that display:
* the current time;
* the name of the file the top line was pulled from;
* the log format for the top line;
* the current view;
* the line number for the top line in the display;
* the current search hit and the total number of hits;
* the number of lines not displayed because of filtering.
Finally, the last line on the display is where you can enter search
patterns and execute internal commands, such as converting a
unix-timestamp into a human-readable date. The command-line is
implemented using the readline library, so the usual set of keyboard
shortcuts are available. Most commands and searches also support
tab-completion.
The body of the display is also used to display other content, such
as: the help file, histograms of the log messages over time, and
SQL results. The views are organized into a stack so that any time
you activate a new view with a key press or command, the new view
is pushed onto the stack. Pressing the same key again will pop the
view off of the stack and return you to the previous view. Note
that you can always use 'q' to pop the top view off of the stack.
KEY BINDINGS
============
Views
-----
? View/leave this help message.
q Leave the current view or quit the program when in
the log file view.
Q Similar to 'q', except it will try to sync the top time
between the current and former views. For example, when
leaving the spectrogram view with 'Q', the top time in that
view will be matched to the top time in the log view.
a/A Restore the view that was previously popped with 'q/Q'.
The 'A' hotkey will try to match the top times between the
two views.
X Close the current text file or log file.
Spatial Navigation
------------------
g/home Move to the top of the file.
G/end Move to the end of the file. If the view is already
at the end, it will move to the last line.
space/pgdn Move down a page.
b/bs/pgup Move up a page.
j/cr/down-arrow Move down a line.
k/up-arrow Move up a line.
h/left-arrow Move to the left. In the log view, moving left will reveal
the source log file names for each line. Pressing again
will reveal the full path.
l/right-arrow Move to the right.
H/Shift+left Move to the left by a smaller increment.
L/Shift+right Move to the right by a smaller increment.
e/E Move to the next/previous error.
w/W Move to the next/previous warning.
n/N Move to the next/previous search hit. When pressed
repeatedly within a short time, the view will move at
least a full page at a time instead of moving to the
next hit.
f/F Move to the next/previous file. In the log view, this
moves to the next line from a different file. In the
text view, this rotates the view to the next file.
>/< Move horizontally to the next/previous search hit.
o/O Move forward/backward to the log message with a matching
'operation ID' (opid) field.
u/U Move forward/backward through any user bookmarks
you have added using the 'm' key. This hotkey will
also jump to the start of any log partitions that have
been created with the 'partition-name' command.
y/Y Move forward/backward through the log view based on the
"log_line" column in the SQL result view.
s/S Move to the next/previous "slow down" in the log message
rate. A slow down is detected by measuring how quickly
the message rate has changed over the previous several
messages. For example, if one message is logged every
second for five seconds and then the last message arrives
five seconds later, the last message will be highlighted
as a slow down.
Chronological Navigation
------------------------
d/D Move forward/backward 24 hours from the current
position in the log file.
1-6/Shift 1-6 Move to the next/previous n'th ten minute of the
hour. For example, '4' would move to the first
log line in the fortieth minute of the current
hour in the log. And, '6' would move to the next
hour boundary.
0/Shift 0 Move to the next/previous day boundary.
r/R Move forward/backward based on the relative time that
was last used with the 'goto' command. For example,
executing ':goto a minute later' will move the log view
forward a minute and then pressing 'r' will move it
forward a minute again. Pressing 'R' will then move the
view in the opposite direction, so backwards a minute.
Bookmarks
---------
m Mark/unmark the line at the top of the display.
The line will be highlighted with reverse video to
indicate that it is a user bookmark. You can use
the 'u' hotkey to iterate through marks you have
added.
M Mark/unmark all the lines between the top of the
display and the last line marked/unmarked.
J Mark/unmark the next line after the previously
marked line.
K Like 'J' except it toggles the mark on the
previous line.
c Copy the marked text to the X11 selection buffer or OS X
clipboard.
C Clear all marked lines.
Display options
---------------
P Switch to/from the pretty-printed view of the log or text
files currently displayed. In this view, structured data,
such as XML, will be reformatted to make it easier to read.
t Switch to/from the text file view. The text file view is
for any files that are not recognized as log files.
Ctrl-L (Lo-fi mode) Exit screen-mode and write the
displayed log lines in plain text to the terminal
until a key is pressed. Useful for copying long lines
from the terminal without picking up any of the extra
decorations.
T Toggle the display of the "elapsed time" column that shows
the time elapsed since the beginning of the logs or the
offset from the previous bookmark. Sharp changes in the
message rate are highlighted by coloring the separator
between the time column and the log message. A red
highlight means the message rate has slowed down and green
means it has sped up. You can use the "s/S" hotkeys to
scan through the slow downs.
i View/leave a histogram of the log messages over
time. The histogram counts the number of
displayed log lines for each bucket of time. The
bars are layed out horizontally with colored
segments representing the different log levels.
You can use the 'z' hotkey to change the size of
the time buckets (e.g. ten minutes, one hour, one
day).
I Switch between the log and histogram views while
keeping the time displayed at the top of each view
in sync. For example, if the top line in the log
view is "11:40", hitting 'I' will switch to the
histogram view and scrolled to display "11:00" at
the top (if the zoom level is hours).
z/Shift Z Zoom in or out one step in the histogram view.
v Switch to/from the SQL result view.
V Switch between the log and SQL result views while
keeping the top line number in the log view in
sync with the log_line column in the SQL view.
For example, doing a query that selects for
"log_idle_msecs" and "log_line", you can move the
top of the SQL view to a line and hit 'V' to switch
to the log view and move to the line number that was
selected in the "log_line" column. If there is no
"log_line" column, lnav will find the first column with
a timestamp and move to corresponding time in the log
view.
TAB/Shift+TAB In the SQL result view, cycle through the columns that
are graphed. Initially, all number values are displayed
in a stacked graph. Pressing TAB will change the display
to only graph the first column. Repeatedly pressing TAB
will cycle through the columns until they are all graphed
again.
p In the log view: enable or disable the display of the
fields that the log message parser knows about or has
discovered. This overlay is temporarily enabled when the
semicolon key (;) is pressed so that it is easier to write
queries.
In the DB view: enable or disable the display of values
in columns containing JSON-encoded values in the top row.
The overlay will display the JSON-Pointer reference and
value for all fields in the JSON data.
CTRL-W Toggle word-wrapping.
CTRL-P Show/hide the data preview panel that may be opened when
entering commands or SQL queries.
x Toggle the hiding of log message fields. The hidden fields
will be replaced with three bullets and highlighted in
yellow.
F2 Toggle mouse support.
Query
-----
/<regexp> Start a search for the given regular expression.
The search is live, so when there is a pause in
typing, the currently running search will be
canceled and a new one started. The first ten lines
that match the search will be displayed in the preview
window at the bottom of the view. History is
maintained for your searches so you can rerun them
easily. Words that are currently displayed are also
available for tab-completion, so you can easily
search for values without needing to copy-and-paste
the string. If there is an error encountered while
trying to interpret the expression, the error will
be displayed in red on the status line. While the
search is active, the 'hits' field in the status
line will be green, when finished it will turn
back to black.
Note: The regular expression format used by is PCRE
(Perl-Compatible Regular Expressions). For example,
if you wanted to search for ethernet device names,
regardless of their ID number, you can type:
eth\\d+
You can find more information about Perl regular
expressions at:
http://perldoc.perl.org/perlre.html
If the search string is not valid PCRE, a search
is done for the exact string instead of doing a
regex search.
:<command> Execute an internal command. The commands are
listed below. History is also supported in this
context as well as tab-completion for commands and
some arguments. The result of the command
replaces the command you typed.
;<sql> Execute an SQL query. Most supported log file
formats provide a sqlite virtual table backend
that can be used in queries. See the SQL section
below for more information.
|<script> [arg1 .. argN]
Execute an lnav script contained in a format directory
(e.g. \~/.lnav/formats/default). The script can contain
lines starting with ':', ';', or '|' to execute commands,
SQL queries or execute other files in lnav. Any values
after the script name are treated as arguments can be
referenced in the script using '\$1', '\$2', and so on, like
in a shell script.
CTRL+] Abort command-line entry started with '/', ':', ';', or '|'.
Session
-------
CTRL-R Reset the session state. This will save the current
session state (filters, highlights) and then reset the
state to the factory default.
MOUSE SUPPORT (experimental)
============================
If you are using Xterm, or a compatible terminal, you can use the mouse to
mark lines of text and move the view by grabbing the scrollbar.
NOTE: You need to manually enable this feature by setting the LNAV_EXP
environment variable to "mouse". F2 toggles mouse support.
COMMANDS
========
help Switch to this help text view.
adjust-log-time <date>
Change the time of the top log line to the given time.
All other log lines in the same file will also be
adjusted using the same offset. After the adjustment,
the displayed timestamp will be rewritten to the new
time and highlighted with a magenta color.
This command is useful for lining up log files that
have timestamps from different machines.
unix-time <secs-or-date>
Convert a unix-timestamp in seconds to a
human-readable form or vice-versa.
BEWARE OF TIMEZONE DIFFERENCES.
current-time Print the current time in human-readable form and
as a unix-timestamp.
goto <line#|N%|abs-time|relative-time>
Go to the given line number, N percent into the
file, or the given timestamp in the log view. If the
line number is negative, it is considered an offset
from the last line. Relative time values, like
'a minute ago', 'an hour later', and many other formats
are supported. When using a relative time, the 'r/R'
hotkeys can be used to move the same amount again or in
the same amount in the opposite direction.
relative-goto <line#|N%>
Move the current view up or down by the given amount.
comment <message>
Add a comment to the top line in the log view. The
comment will be saved in the session and will be available
the next time the file is loaded. Searches will also scan
the comment for any matches.
clear-comment Clear the comment that is attached to the top line in the
log view.
tag <tag1> [<tag2> [... <tagN>]]
Attach a tag to the top line in the log view. The tags are
prefixed with a '#', if they don't have one already. And,
like comments, they are saved in the session and
searchable.
untag <tag1> [<tag2> [... <tagN>]]
Detach a tag from the top line in the log view.
delete-tags <tag1> [<tag2> [... <tagN>]]
Detach the tags from all log lines.
next-mark error|warning|search|user|file|meta
Move to the next bookmark of the given type in the
current view.
prev-mark error|warning|search|user|file|meta
Move to the previous bookmark of the given type in the
current view.
hide-lines-before <abs-time|relative-time>
Hide lines that are before the given time. The given
time can be absolute (e.g. 2015-10-11)
The hidden lines can be shown again with the
'show-lines-before-and-after' command.
hide-lines-after <abs-time|relative-time>
Hide lines that are after the given time. The time can
The hidden lines can be shown again with the
'show-lines-before-and-after' command.
show-lines-before-and-after
Show lines that were hidden by the 'hide-lines' commands.
hide-fields <field-name> [<field-name2> ... <field-nameN>]
Hide large log message fields by replacing them with an
ellipsis. You can quickly switching between showing and
hiding hidden fields using the 'x' hotkey.
show-fields <field-name> [<field-name2> ... <field-nameN>]
Show log messages fields that were previously hidden with
the ':hide-fields' command.
highlight <regex> Highlight strings that match the given regular
expression.
clear-highlight <regex>
Clear an existing highlight created with the 'highlight'
command.
filter-in <regex> Only display lines that match the given regular
expression. This command can be used multiple
times to add more lines to the display. The number
of lines that are filtered out will be shown in the
bottom status bar as 'Not Shown'. Note that filtering
only works in the log and plain text views. There is also
a limit of 32 filters per-view at any one time.
filter-out <regex>
Do not display lines that match the given regular
expression. This command can be used multiple
times to remove more lines from the display. If a
'filter-in' expression is also active, it takes
priority and the filter-out will remove lines that
were matched by the 'filter-in'. The number
of lines that are filtered out will be shown in the
bottom status bar as 'Not Shown'. Note that filtering
only works in the log and plain text views. There is also
a limit of 32 filters per-view at any one time. While
entering the regular expression at the command-prompt, the
matches in the current text view will be highlighted in red
after a short delay.
disable-filter <regex>
Disable an active 'filter-in' or 'filter-out'
expression.
enable-filter <regex>
Enable a inactive 'filter-in' or 'filter-out'
expression.
delete-filter <regex>
Permanently delete a filter.
set-min-log-level <level>
Set the minimum level to display in the log view.
You can use TAB to view the possible values.
disable-word-wrap Disable word wrapping in the log and text file views.
enable-word-wrap Enable word wrapping in the log and text file views.
open <filename>[:<line>]
Open the given file within lnav and, if it is a
text file, switch to the text view and jump to
the given line number.
close Close the current text file or log file. You can also
close the current file by pressing 'X'.
spectrogram <field-name>
Generate a spectrogram for a numeric log message field or
SQL result column. The spectrogram view displays the range
of possible values of the field on the horizontal axis and
time on the vertical axis. The horizontal axis is split
into buckets where each bucket counts how many log messages
contained the field with a value in that range. The buckets
are colored based on the count in the bucket: green means
low, yellow means medium, and red means high. The exact
ranges for the colors is computed automatically and
displayed in the middle of the top line of the view. The
minimum and maximum values for the field are displayed in
the top left and right sides of the view, respectively.
append-to <file> Append any marked lines to the given file.
write-to <file> Write any marked lines to the given file. Use '-' to
write the lines to the terminal.
write-csv-to <file>
Write the results of a SQL query to a CSV-formatted file.
When running in non-interactive mode, a dash can be used
to write to standard out. Use '-' to write the data to
the terminal.
write-json-to <file>
Write the results of a SQL query to a JSON-formatted file.
The contents of the file will be an array of objects with
each column in the query being a field in the objects.
When running in non-interactive mode, a dash can be used
to write to standard out. Use '-' to write the data to
the terminal.
pipe-to <shell-cmd>
Send the currently marked lines to the given shell command
for processing and open the resulting file for viewing.
pipe-line-to <shell-cmd>
Send the top log message to the given shell command
for processing and open the resulting file for viewing.
The known and discovered message fields are available as
environment variables. For example, log_procname in a
syslog message.
session <cmd> Add the given command to the session file
(\~/.lnav/session). Any commands listed in the session file
are executed on startup. Only the highlight, word-wrap, and
filter-related commands can be added to the session file.
create-logline-table <table-name>
Create an SQL table using the top line of the log view
as a template. See the "SQL QUERIES" and "DYNAMIC LOG
LINE TABLE" sections below for more information.
delete-logline-table <table-name>
Delete an SQL table created by the 'create-logline-table'
command.
create-search-table <table-name> [<regex>]
Create an SQL table that extracts information from logs
using the provided regular expression or the last search
that was done. Any captures in the expression will be
used as columns in the SQL table. If the capture is named,
that name will be used as the column name, otherwise the
column name will be of the form 'col_N'.
delete-search-table <table-name>
Delete a table that was created with create-search-table.
switch-to-view <view-name>
Switch the display to the given view, which can be one of:
help, log, text, histogram, db, and schema.
zoom-to <zoom-level>
Change the histogram zoom level to the given value, which
can be one of: day, 4-hour, hour, 10-minute, minute
redraw Force redraw the window.
partition-name <name>
Mark the top line in the log view as the start of a new
partition with the given name. The current partition name
will be reflected in the top status bar next to the current
time as well as being available in the 'log_part' column
of the SQL log tables. Partitions can be used to make it
easier to query subsections of log messages.
clear-partition
Clear the partition the top line is a part of.
echo [-n] <msg> Display the given message. Useful for scripts to message
the user. The '-n' option leaves out the new line at the
end of the message.
eval <cmd|query|file>
Execute the given command, query, or file after doing
environment variable substitution. The argument to this
command should start with a ':', ';', or '|' signify the
type of action to perform (command, SQL query, execute
script).
pt-min-time [<date>|<relative-time>]
Set/get the minimum time range for any papertrail queries.
Absolute or relative time values can be specified.
pt-max-time [<date>|<relative-time>]
Set/get the maximum time range for any papertrail queries.
Absolute or relative time values can be specified.
config <option> [value]
Set/get the value of a configuration option.
reset-config <option>
Reset a configuration option to the default value. Use
'*' to reset all options.
save-config Save the current configuration state to:
\~/.lnav/config.json
quit Quit lnav.
SQL QUERIES (experimental)
===========
Lnav has support for performing SQL queries on log files using the
Sqlite3 "virtual" table feature. For all supported log file types,
lnav will create tables that can be queried using the subset of SQL
that is supported by Sqlite3. For example, to get the top ten URLs
being accessed in any loaded Apache log files, you can execute:
;select cs_uri_stem, count(*) as total from access_log
group by cs_uri_stem order by total desc limit 10;
The query result view shows the results and graphs any numeric
values found in the result, much like the histogram view.
The builtin set of log tables are listed below. Note that only the
log messages that match a particular format can be queried by a
particular table. You can find the file format and table name for
the top log message by looking in the upper right hand corner of the
log file view.
Some commonly used format tables are:
access_log Apache common access log format
syslog_log Syslog format
strace_log Strace log format
generic_log 'Generic' log format. This table contains messages
from files that have a very simple format with a
leading timestamp followed by the message.
NOTE: You can get a dump of the schema for the internal tables, and
any attached databases, by running the '.schema' SQL command.
The columns available for the top log line in the view will
automatically be displayed after pressing the semicolon (;) key.
All log tables contain at least the following columns:
log_line The line number in the file, starting at zero.
log_part The name of the partition. You can change this
column using an UPDATE SQL statement or with the
'partition-name' command. After a value is set,
the following log messages will have the same
partition name up until another name is set.
log_time The time of the log entry.
log_idle_msecs The amount of time, in milliseconds, between the
current log message and the previous one.
log_level The log level (e.g. info, error, etc...).
log_mark The bookmark status for the line. This column
can be written to using an UPDATE query.
log_path The full path to the file.
log_text The raw line of text. Note that this column is
not included in the result of a 'select *', but
it does exist.
The following tables include the basic columns as listed above and
include a few more columns since the log file format is more
structured.
syslog_log
log_hostname The hostname the message was received from.
log_procname The name of the process that sent the message.
log_pid The process ID of the process that sent the message.
access_log (The column names are the same as those in the
Microsoft LogParser tool.)
c_ip The client IP address.
cs_username The client user name.
cs_method The HTTP method.
cs_uri_stem The stem portion of the URI.
cs_uri_query The query portion of the URI.
cs_version The HTTP version string.
sc_status The status number returned to the client.
sc_bytes The number of bytes sent to the client.
cs_referrer The URL of the referring page.
cs_user_agent The user agent string.
strace_log (Currently, you need to run strace with the
"-tt -T" options so there are timestamps for
each function call.)
funcname The name of the syscall.
result The result code.
duration The amount of time spent in the syscall.
arg0 - arg9 The arguments passed to the syscall.
These tables are created dynamically and not stored in memory or on
disk. If you would like to persist some information from the tables,
you can attach another database and create tables in that database.
For example, if you wanted to save the results from the earlier
example of a top ten query into the "/tmp/topten.db" file, you can do:
;attach database "/tmp/topten.db" as topten;
;create table topten.foo as select cs_uri_stem, count(*) as total
from access_log group by cs_uri_stem order by total desc
limit 10;
DYNAMIC LOG LINE TABLE (experimental)
======================
(NOTE: This feature is still very new and not completely reliable yet,
use with care.)
For log formats that lack message structure, lnav can parse the log
message and attempt to extract any data fields that it finds. This
feature is available through the "logline" log table. This table is
dynamically created and defined based on the message at the top of
the log view. For example, given the following log message from "sudo",
lnav will create the "logline" table with columns for "TTY", "PWD",
"USER", and "COMMAND":
May 24 06:48:38 Tim-Stacks-iMac.local sudo[76387]: stack : TTY=ttys003 ;
PWD=/Users/stack/github/lbuild ; USER=root ;
COMMAND=/bin/echo Hello, World!
Queries executed against this table will then only return results for
other log messages that have the same format. So, if you were to
execute the following query while viewing the above line, you might
get the following results:
;select USER,COMMAND from logline;
USER | COMMAND
---- | -------------------------
root | /bin/echo Hello, World!
mal | /bin/echo Goodbye, World!
The log parser works by examining each message for key/value pairs
separated by an equal sign (=) or a colon (:). For example, in the
previous example of a "sudo" message, the parser sees the "USER=root"
string as a pair where the key is "USER" and the value is "root".
If no pairs can be found, then anything that looks like a value is
extracted and assigned a numbered column. For example, the following
line is from "dhcpd":
Sep 16 22:35:57 drill dhcpd: DHCPDISCOVER from 00:16:ce:54:4e:f3 via hme3
In this case, the lnav parser recognizes that "DHCPDISCOVER", the MAC
address and the "hme3" device name are values and not normal words. So,
it builds a table with three columns for each of these values. The
regular words in the message, like "from" and "via", are then used to
find other messages with a similar format.
If you would like to execute queries against log messages of different
formats at the same time, you can use the 'create-logline-table' command
to permanently create a table using the top line of the log view as a
template.
OTHER SQL FEATURES
==================
Environment variables can be used in SQL statements by prefixing the
variable name with a dollar-sign (\$). For example, to read the value of
the HOME variable, you can do:
;SELECT \$HOME;
To select the syslog messages that have a hostname field that is equal
to the HOSTNAME variable:
;SELECT * FROM syslog_log WHERE log_hostname = \$HOSTNAME;
NOTE: Variable substitution is done for fields in the query and is not
a plain text substitution. For example, the following statement
WILL NOT WORK:
;SELECT * FROM \$TABLE_NAME; -- Syntax error
Access to lnav's environment variables is also available via the "environ"
table. The table has two columns (name, value) and can be read and written
to using SQL SELECT, INSERT, UPDATE, and DELETE statements. For example,
to set the "FOO" variable to the value "BAR":
;INSERT INTO environ SELECT 'FOO', 'BAR';
As a more complex example, you can set the variable "LAST" to the last
syslog line number by doing:
;INSERT INTO environ SELECT 'LAST', (SELECT max(log_line) FROM syslog_log);
A delete will unset the environment variable:
;DELETE FROM environ WHERE name='LAST';
The table allows you to easily use the results of a SQL query in lnav
commands, which is especially useful when scripting lnav.
PAPERTRAIL INTEGRATION
======================
Papertrail is a log management service with free and paid plans at:
http://papertrailapp.com
To configure lnav to communicate with the papertrail service, you will
need to set the PAPERTRAIL_API_TOKEN environment variable. You can
get your API token from your user profile, available here:
https://papertrailapp.com/user/edit
Searching papertrail using lnav can be done by prefixing the search terms
with "pt:" and passing the value as a file name. For example, to search
for log messages with the string 'Critical Error' when starting lnav you
can do the following:
\$ setenv PAPERTRAIL_API_TOKEN xxxxxxxxx
\$ lnav "pt:'Critical Error'"
If lnav is already started, you can use the ':open' command like so:
:open pt:'Critical Error'
If you just want to tail your logs in papertrail, you can pass an empty
search string (i.e. "pt:").
Only one papertrail search can be active at a time. So, if an ':open'
is done with a new query, the previous query will be closed first.
CONTACT
=======
For more information, visit the lnav website at:
http://lnav.org
For support questions, email:
lnav@googlegroups.com
REFERENCE
=========
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