SQLite Extensions Reference¶
To make it easier to analyze log data from within lnav, there are several built-in extensions that provide extra functions and collators beyond those provided by SQLite. The majority of the functions are from the extensions-functions.c file available from the sqlite.org web site.
Tip: You can include a SQLite database file on the command-line and use lnav‘s interface to perform queries. The database will be attached with a name based on the database file name.
A SQL command is an internal macro implemented by lnav.
- .schema - Open the schema view. This view contains a dump of the schema for the internal tables and any tables in attached databases.
Environment variables can be accessed in queries using the usual syntax of “$VAR_NAME”. For example, to read the value of the “USER” variable, you can write:
Basic mathematical functions:
- sign(n) - Return one of 3 possibilities +1,0 or -1 when the argument is respectively positive, 0 or negative.
- degrees - Convert radians to degrees
- radians - Convert degrees to radians
Additional string comparison and manipulation functions:
- difference(s1,s2) - Computes the number of different characters between the soundex value fo 2 strings.
- replicate(s,n) - Given a string (s) in the first argument and an integer (n) in the second returns the string that constains s contatenated n times.
- proper(s) - Ensures that the words in the given string have their first letter capitalized and the following letters are lower case.
- charindex(s1,s2), charindex(s1,s2,n) - Given 2 input strings (s1,s2) and an integer (n) searches from the nth character for the string s1. Returns the position where the match occured. Characters are counted from 1. 0 is returned when no match occurs.
- leftstr(s,n) - Given a string (s) and an integer (n) returns the n leftmost (UTF-8) characters if the string has a length<=n or is NULL this function is NOP.
- rightstr(s,n) - Given a string (s) and an integer (n) returns the n rightmost (UTF-8) characters if the string has a length<=n or is NULL this function is NOP
- reverse(s) - Given a string returns the same string but with the characters in reverse order.
- padl(s,n) - Given an input string (s) and an integer (n) adds spaces at the beginning of (s) until it has a length of n characters. When s has a length >=n it’s a NOP. padl(NULL) = NULL
- padr(s,n) - Given an input string (s) and an integer (n) appends spaces at the end of s until it has a length of n characters. When s has a length >=n it’s a NOP. padr(NULL) = NULL
- padc(s,n) - Given an input string (s) and an integer (n) appends spaces at the end of s and adds spaces at the begining of s until it has a length of n characters. Tries to add has many characters at the left as at the right. When s has a length >=n it’s a NOP. padc(NULL) = NULL
- strfilter(s1,s2) - Given 2 string (s1,s2) returns the string s1 with the characters NOT in s2 removed assumes strings are UTF-8 encoded.
- regexp(re,s) - Return 1 if the regular expression ‘re’ matches the given string.
- regexp_replace(str, re, repl) - Replace the portions of the given string that match the regular expression with the replacement string. NOTE: The arguments for the string and the regular expression in this function are reversed from the plain regexp() function. This is to be somewhat compatible with functions in other database implementations.
- startswith(s1,prefix) - Given a string and prefix, return 1 if the string starts with the given prefix.
- endswith(s1,suffix) - Given a string and suffix, return 1 if the string ends with the given suffix.
- regexp_match(re,str) - Match and extract values from a string using a regular expression. The “re” argument should be a PCRE with captures. If there is a single capture, that captured value will be directly returned. If there is more than one capture, a JSON object will be returned with field names matching the named capture groups or ‘col_N’ where ‘N’ is the index of the capture. If the expression does not match the string, NULL is returned.
- extract(str) - Parse and extract values from a string using the same algorithm as the logline table (see Extracting Data). The discovered data is returned as a JSON-object that you can do further processing on.
File path manipulation functions:
- basename(s) - Return the file name part of a path.
- dirname(s) - Return the directory part of a path.
- joinpath(s1,s2,...) - Return the arguments joined together into a path.
Network information functions:
- gethostbyname - Convert a host name into an IP address. The host name could not be resolved, the input value will be returned.
- gethostbyaddr - Convert an IPv4/IPv6 address into a host name. If the reverse lookup fails, the input value will be returned.
- jget(json, json_ptr) - Get the value from the JSON-encoded string in first argument that is referred to by the JSON-Pointer in the second.
- json_group_object(key0, value0, ... keyN, valueN) - An aggregate function that creates a JSON-encoded object from the key value pairs given as arguments.
- json_group_array(value0, ... valueN) - An aggregate function that creates a JSON-encoded array from the values given as arguments.
- timeslice(t, s) - Given a time stamp (t) and a time slice (s), return a timestamp for the bucket of time that the timestamp falls in. For example, with the timestamp “2015-03-01 11:02:00’ and slice ‘5min’ the returned value will be ‘2015-03-01 11:00:00’. This function can be useful when trying to group together log messages into buckets.
The following functions can be used to access lnav‘s internal state:
- log_top_line() - Return the line number at the top of the log view.
- log_top_datetime() - Return the timestamp of the line at the top of the log view.
- naturalcase - Compare strings “naturally” so that number values in the string are compared based on their numeric value and not their character values. For example, “foo10” would be considered greater than “foo2”.
- naturalnocase - The same as naturalcase, but case-insensitive.
- ipaddress - Compare IPv4/IPv6 addresses.