Provided by: jq_1.6-1_amd64 bug

NAME

       jq - Command-line JSON processor

SYNOPSIS

       jq [options...] filter [files...]

       jq  can  transform  JSON  in various ways, by selecting, iterating, reducing and otherwise
       mangling JSON documents. For instance, running the command jq  ´map(.price)  |  add´  will
       take an array of JSON objects as input and return the sum of their "price" fields.

       jq  can  accept  text  input  as  well, but by default, jq reads a stream of JSON entities
       (including numbers and other literals) from stdin. Whitespace is only needed  to  separate
       entities such as 1 and 2, and true and false. One or more files may be specified, in which
       case jq will read input from those instead.

       The options are described in the #INVOKING-JQ  section;  they  mostly  concern  input  and
       output formatting. The filter is written in the jq language and specifies how to transform
       the input file or document.

FILTERS

       A jq program is a "filter": it takes an input, and produces an output. There are a lot  of
       builtin  filters for extracting a particular field of an object, or converting a number to
       a string, or various other standard tasks.

       Filters can be combined in various ways - you can pipe  the  output  of  one  filter  into
       another filter, or collect the output of a filter into an array.

       Some  filters  produce  multiple  results,  for instance there´s one that produces all the
       elements of its input array. Piping that filter into a second runs the second  filter  for
       each  element  of the array. Generally, things that would be done with loops and iteration
       in other languages are just done by gluing filters together in jq.

       It´s important to remember that every filter has an input and  an  output.  Even  literals
       like "hello" or 42 are filters - they take an input but always produce the same literal as
       output. Operations that combine two filters, like addition, generally feed the same  input
       to both and combine the results. So, you can implement an averaging filter as add / length
       - feeding the input array both to the add filter and the length filter and then performing
       the division.

       But that´s getting ahead of ourselves. :) Let´s start with something simpler:

INVOKING JQ

       jq  filters  run  on  a  stream  of  JSON data. The input to jq is parsed as a sequence of
       whitespace-separated JSON values which are passed through the provided  filter  one  at  a
       time.  The  output(s)  of  the  filter are written to standard out, again as a sequence of
       whitespace-separated JSON data.

       Note: it is important to mind the shell´s quoting rules. As a general rule  it´s  best  to
       always  quote  (with  single-quote characters) the jq program, as too many characters with
       special meaning to jq are also shell meta-characters. For example, jq "foo" will  fail  on
       most  Unix  shells  because  that  will  be  the same as jq foo, which will generally fail
       because foo is not defined. When using the Windows command shell (cmd.exe)  it´s  best  to
       use double quotes around your jq program when given on the command-line (instead of the -f
       program-file option), but then double-quotes in the jq program need backslash escaping.

       You can affect how jq reads and writes  its  input  and  output  using  some  command-line
       options:

       ○   --version:

           Output the jq version and exit with zero.

       ○   --seq:

           Use  the application/json-seq MIME type scheme for separating JSON texts in jq´s input
           and output. This means that an ASCII RS (record separator) character is printed before
           each  value on output and an ASCII LF (line feed) is printed after every output. Input
           JSON texts that  fail  to  parse  are  ignored  (but  warned  about),  discarding  all
           subsequent input until the next RS. This mode also parses the output of jq without the
           --seq option.

       ○   --stream:

           Parse the input in streaming  fashion,  outputing  arrays  of  path  and  leaf  values
           (scalars  and  empty  arrays or empty objects). For example, "a" becomes [[],"a"], and
           [[],"a",["b"]] becomes [[0],[]], [[1],"a"], and [[1,0],"b"].

           This is useful for  processing  very  large  inputs.  Use  this  in  conjunction  with
           filtering and the reduce and foreach syntax to reduce large inputs incrementally.

       ○   --slurp/-s:

           Instead of running the filter for each JSON object in the input, read the entire input
           stream into a large array and run the filter just once.

       ○   --raw-input/-R:

           Don´t parse the input as JSON. Instead, each line of text is passed to the filter as a
           string.  If  combined with --slurp, then the entire input is passed to the filter as a
           single long string.

       ○   --null-input/-n:

           Don´t read any input at all! Instead, the filter is run once using null as the  input.
           This  is  useful  when  using jq as a simple calculator or to construct JSON data from
           scratch.

       ○   --compact-output / -c:

           By default, jq pretty-prints JSON output.  Using  this  option  will  result  in  more
           compact output by instead putting each JSON object on a single line.

       ○   --tab:

           Use a tab for each indentation level instead of two spaces.

       ○   --indent n:

           Use the given number of spaces (no more than 8) for indentation.

       ○   --color-output / -C and --monochrome-output / -M:

           By  default,  jq  outputs  colored  JSON if writing to a terminal. You can force it to
           produce color even if writing to a pipe or a file using -C, and disable color with -M.

           Colors can be configured with the JQ_COLORS environment variable (see below).

       ○   --ascii-output / -a:

           jq usually outputs non-ASCII Unicode codepoints as UTF-8, even if the input  specified
           them  as  escape  sequences  (like  "\u03bc").  Using this option, you can force jq to
           produce pure ASCII output with every non-ASCII character replaced with the  equivalent
           escape sequence.

       ○   --unbuffered

           Flush  the  output  after  each JSON object is printed (useful if you´re piping a slow
           data source into jq and piping jq´s output elsewhere).

       ○   --sort-keys / -S:

           Output the fields of each object with the keys in sorted order.

       ○   --raw-output / -r:

           With this option, if the filter´s result is a string then it will be written  directly
           to  standard output rather than being formatted as a JSON string with quotes. This can
           be useful for making jq filters talk to non-JSON-based systems.

       ○   --join-output / -j:

           Like -r but jq won´t print a newline after each output.

       ○   -f filename / --from-file filename:

           Read filter from the file rather than from a command line, like awk´s -f  option.  You
           can also use ´#´ to make comments.

       ○   -Ldirectory / -L directory:

           Prepend  directory  to  the  search  list  for modules. If this option is used then no
           builtin search list is used. See the section on modules below.

       ○   -e / --exit-status:

           Sets the exit status of jq to 0 if the last output values was neither false nor  null,
           1  if the last output value was either false or null, or 4 if no valid result was ever
           produced. Normally jq exits with 2 if there was any usage problem or system  error,  3
           if there was a jq program compile error, or 0 if the jq program ran.

           Another way to set the exit status is with the halt_error builtin function.

       ○   --arg name value:

           This  option  passes a value to the jq program as a predefined variable. If you run jq
           with --arg foo bar, then $foo is available in the program and  has  the  value  "bar".
           Note that value will be treated as a string, so --arg foo 123 will bind $foo to "123".

           Named arguments are also available to the jq program as $ARGS.named.

       ○   --argjson name JSON-text:

           This option passes a JSON-encoded value to the jq program as a predefined variable. If
           you run jq with --argjson foo 123, then $foo is available in the program and  has  the
           value 123.

       ○   --slurpfile variable-name filename:

           This  option  reads  all  the  JSON  texts in the named file and binds an array of the
           parsed JSON values to the given global variable. If you run jq  with  --slurpfile  foo
           bar,  then $foo is available in the program and has an array whose elements correspond
           to the texts in the file named bar.

       ○   --rawfile variable-name filename:

           This option reads in the named file  and  binds  its  contents  to  the  given  global
           variable.  If you run jq with --rawfile foo bar, then $foo is available in the program
           and has a string whose contents are to the texs in the file named bar.

       ○   --argfile variable-name filename:

           Do not use. Use --slurpfile instead.

           (This option is like --slurpfile, but when the file has just one text,  then  that  is
           used, else an array of texts is used as in --slurpfile.)

       ○   --args:

           Remaining  arguments  are  positional  string arguments. These are available to the jq
           program as $ARGS.positional[].

       ○   --jsonargs:

           Remaining arguments are positional JSON text arguments. These are available to the  jq
           program as $ARGS.positional[].

       ○   --run-tests [filename]:

           Runs the tests in the given file or standard input. This must be the last option given
           and does not honor all preceding options. The input consists of comment  lines,  empty
           lines,  and  program  lines followed by one input line, as many lines of output as are
           expected (one per output), and a terminating empty  line.  Compilation  failure  tests
           start  with  a  line  containing  only "%%FAIL", then a line containing the program to
           compile, then a line containing an error message to compare to the actual.

           Be warned that this option can change backwards-incompatibly.

BASIC FILTERS

   Identity: .
       The absolute simplest filter is . . This is a filter that takes its input and produces  it
       unchanged as output. That is, this is the identity operator.

       Since  jq by default pretty-prints all output, this trivial program can be a useful way of
       formatting JSON output from, say, curl.

           jq ´.´
              "Hello, world!"
           => "Hello, world!"

   Object Identifier-Index: .foo, .foo.bar
       The simplest useful filter is .foo. When given a JSON object (aka dictionary or  hash)  as
       input, it produces the value at the key "foo", or null if there´s none present.

       A filter of the form .foo.bar is equivalent to .foo|.bar.

       This  syntax  only works for simple, identifier-like keys, that is, keys that are all made
       of alphanumeric characters and underscore, and which do not start with a digit.

       If the key contains special characters, you need to surround it with  double  quotes  like
       this: ."foo$", or else .["foo$"].

       For  example  .["foo::bar"]  and  .["foo.bar"] work while .foo::bar does not, and .foo.bar
       means .["foo"].["bar"].

           jq ´.foo´
              {"foo": 42, "bar": "less interesting data"}
           => 42

           jq ´.foo´
              {"notfoo": true, "alsonotfoo": false}
           => null

           jq ´.["foo"]´
              {"foo": 42}
           => 42

   Optional Object Identifier-Index: .foo?
       Just like .foo, but does not output even an error when . is not an array or an object.

           jq ´.foo?´
              {"foo": 42, "bar": "less interesting data"}
           => 42

           jq ´.foo?´
              {"notfoo": true, "alsonotfoo": false}
           => null

           jq ´.["foo"]?´
              {"foo": 42}
           => 42

           jq ´[.foo?]´
              [1,2]
           => []

   Generic Object Index: .[<string>]
       You can also look up fields of an object using syntax  like  .["foo"]  (.foo  above  is  a
       shorthand version of this, but only for identifier-like strings).

   Array Index: .[2]
       When the index value is an integer, .[<value>] can index arrays. Arrays are zero-based, so
       .[2] returns the third element.

       Negative indices are allowed, with -1 referring to the last element, -2 referring  to  the
       next to last element, and so on.

           jq ´.[0]´
              [{"name":"JSON", "good":true}, {"name":"XML", "good":false}]
           => {"name":"JSON", "good":true}

           jq ´.[2]´
              [{"name":"JSON", "good":true}, {"name":"XML", "good":false}]
           => null

           jq ´.[-2]´
              [1,2,3]
           => 2

   Array/String Slice: .[10:15]
       The .[10:15] syntax can be used to return a subarray of an array or substring of a string.
       The array returned by .[10:15] will be of length 5, containing the elements from index  10
       (inclusive) to index 15 (exclusive). Either index may be negative (in which case it counts
       backwards from the end of the array), or omitted (in which case it refers to the start  or
       end of the array).

           jq ´.[2:4]´
              ["a","b","c","d","e"]
           => ["c", "d"]

           jq ´.[2:4]´
              "abcdefghi"
           => "cd"

           jq ´.[:3]´
              ["a","b","c","d","e"]
           => ["a", "b", "c"]

           jq ´.[-2:]´
              ["a","b","c","d","e"]
           => ["d", "e"]

   Array/Object Value Iterator: .[]
       If  you  use  the  .[index] syntax, but omit the index entirely, it will return all of the
       elements of an array. Running .[] with the input [1,2,3] will produce the numbers as three
       separate results, rather than as a single array.

       You can also use this on an object, and it will return all the values of the object.

           jq ´.[]´
              [{"name":"JSON", "good":true}, {"name":"XML", "good":false}]
           => {"name":"JSON", "good":true}, {"name":"XML", "good":false}

           jq ´.[]´
              []
           =>

           jq ´.[]´
              {"a": 1, "b": 1}
           => 1, 1

   .[]?
       Like .[], but no errors will be output if . is not an array or object.

   Comma: ,
       If two filters are separated by a comma, then the same input will be fed into both and the
       two filters´ output value streams will be concatenated in order: first, all of the outputs
       produced  by  the  left expression, and then all of the outputs produced by the right. For
       instance, filter .foo, .bar, produces both the "foo" fields and "bar" fields  as  separate
       outputs.

           jq ´.foo, .bar´
              {"foo": 42, "bar": "something else", "baz": true}
           => 42, "something else"

           jq ´.user, .projects[]´
              {"user":"stedolan", "projects": ["jq", "wikiflow"]}
           => "stedolan", "jq", "wikiflow"

           jq ´.[4,2]´
              ["a","b","c","d","e"]
           => "e", "c"

   Pipe: |
       The  |  operator combines two filters by feeding the output(s) of the one on the left into
       the input of the one on the right. It´s pretty much the same as the Unix shell´s pipe,  if
       you´re used to that.

       If  the  one  on  the left produces multiple results, the one on the right will be run for
       each of those results. So, the expression .[] | .foo retrieves the  "foo"  field  of  each
       element of the input array.

       Note that .a.b.c is the same as .a | .b | .c.

       Note  too that . is the input value at the particular stage in a "pipeline", specifically:
       where the . expression appears. Thus .a | . | .b is the same as .a.b,  as  the  .  in  the
       middle refers to whatever value .a produced.

           jq ´.[] | .name´
              [{"name":"JSON", "good":true}, {"name":"XML", "good":false}]
           => "JSON", "XML"

   Parenthesis
       Parenthesis work as a grouping operator just as in any typical programming language.

           jq ´(. + 2) * 5´
              1
           => 15

TYPES AND VALUES

       jq  supports  the  same  set  of  datatypes  as JSON - numbers, strings, booleans, arrays,
       objects (which in JSON-speak are hashes with only string keys), and "null".

       Booleans, null, strings and numbers are written the same way as in javascript.  Just  like
       everything  else  in jq, these simple values take an input and produce an output - 42 is a
       valid jq expression that takes an input, ignores it, and returns 42 instead.

   Array construction: []
       As in JSON, [] is used to construct arrays, as in [1,2,3]. The elements of the arrays  can
       be  any  jq  expression,  including  a pipeline. All of the results produced by all of the
       expressions are collected into one big array. You can use it to construct an array out  of
       a known quantity of values (as in [.foo, .bar, .baz]) or to "collect" all the results of a
       filter into an array (as in [.items[].name])

       Once you understand the "," operator, you can look at jq´s array  syntax  in  a  different
       light:  the  expression [1,2,3] is not using a built-in syntax for comma-separated arrays,
       but is instead applying the [] operator (collect results) to the expression  1,2,3  (which
       produces three different results).

       If  you have a filter X that produces four results, then the expression [X] will produce a
       single result, an array of four elements.

           jq ´[.user, .projects[]]´
              {"user":"stedolan", "projects": ["jq", "wikiflow"]}
           => ["stedolan", "jq", "wikiflow"]

           jq ´[ .[] | . * 2]´
              [1, 2, 3]
           => [2, 4, 6]

   Object Construction: {}
       Like JSON, {} is for constructing objects (aka dictionaries or hashes), as in:  {"a":  42,
       "b": 17}.

       If  the  keys  are "identifier-like", then the quotes can be left off, as in {a:42, b:17}.
       Keys generated by expressions need to be parenthesized, e.g., {("a"+"b"):59}.

       The value can be any expression (although you may need to wrap it in parentheses if it´s a
       complicated  one),  which gets applied to the {} expression´s input (remember, all filters
       have an input and an output).

           {foo: .bar}

       will produce the JSON object {"foo": 42} if given the JSON object {"bar":42, "baz":43}  as
       its  input.  You can use this to select particular fields of an object: if the input is an
       object with "user", "title", "id", and "content" fields  and  you  just  want  "user"  and
       "title", you can write

           {user: .user, title: .title}

       Because that is so common, there´s a shortcut syntax for it: {user, title}.

       If  one  of  the  expressions  produces  multiple  results,  multiple dictionaries will be
       produced. If the input´s

           {"user":"stedolan","titles":["JQ Primer", "More JQ"]}

       then the expression

           {user, title: .titles[]}

       will produce two outputs:

           {"user":"stedolan", "title": "JQ Primer"}
           {"user":"stedolan", "title": "More JQ"}

       Putting parentheses around the key means it will be evaluated as an expression.  With  the
       same input as above,

           {(.user): .titles}

       produces

           {"stedolan": ["JQ Primer", "More JQ"]}

           jq ´{user, title: .titles[]}´
              {"user":"stedolan","titles":["JQ Primer", "More JQ"]}
           => {"user":"stedolan", "title": "JQ Primer"}, {"user":"stedolan", "title": "More JQ"}

           jq ´{(.user): .titles}´
              {"user":"stedolan","titles":["JQ Primer", "More JQ"]}
           => {"stedolan": ["JQ Primer", "More JQ"]}

   Recursive Descent: ..
       Recursively  descends  .,  producing  every  value.  This is the same as the zero-argument
       recurse builtin (see below). This is intended to resemble the XPath // operator. Note that
       ..a  does  not work; use ..|.a instead. In the example below we use ..|.a? to find all the
       values of object keys "a" in any object found "below" ..

       This is particularly useful in conjunction with path(EXP)  (also  see  below)  and  the  ?
       operator.

           jq ´..|.a?´
              [[{"a":1}]]
           => 1

BUILTIN OPERATORS AND FUNCTIONS

       Some  jq  operator  (for  instance,  +) do different things depending on the type of their
       arguments (arrays, numbers, etc.). However, jq never does implicit  type  conversions.  If
       you try to add a string to an object you´ll get an error message and no result.

   Addition: +
       The  operator  +  takes  two  filters,  applies  them both to the same input, and adds the
       results together. What "adding" means depends on the types involved:

       ○   Numbers are added by normal arithmetic.

       ○   Arrays are added by being concatenated into a larger array.

       ○   Strings are added by being joined into a larger string.

       ○   Objects are added by merging, that is, inserting all the  key-value  pairs  from  both
           objects  into  a  single combined object. If both objects contain a value for the same
           key, the object on the right of the + wins. (For recursive merge use the * operator.)

       null can be added to any value, and returns the other value unchanged.

           jq ´.a + 1´
              {"a": 7}
           => 8

           jq ´.a + .b´
              {"a": [1,2], "b": [3,4]}
           => [1,2,3,4]

           jq ´.a + null´
              {"a": 1}
           => 1

           jq ´.a + 1´
              {}
           => 1

           jq ´{a: 1} + {b: 2} + {c: 3} + {a: 42}´
              null
           => {"a": 42, "b": 2, "c": 3}

   Subtraction: -
       As well as normal arithmetic subtraction on numbers, the - operator can be used on  arrays
       to remove all occurrences of the second array´s elements from the first array.

           jq ´4 - .a´
              {"a":3}
           => 1

           jq ´. - ["xml", "yaml"]´
              ["xml", "yaml", "json"]
           => ["json"]

   Multiplication, division, modulo: *, /, and %
       These  infix  operators behave as expected when given two numbers. Division by zero raises
       an error. x % y computes x modulo y.

       Multiplying a string by a number produces the  concatenation  of  that  string  that  many
       times. "x" * 0 produces null.

       Dividing a string by another splits the first using the second as separators.

       Multiplying  two objects will merge them recursively: this works like addition but if both
       objects contain a value for the same key, and the values are objects, the two  are  merged
       with the same strategy.

           jq ´10 / . * 3´
              5
           => 6

           jq ´. / ", "´
              "a, b,c,d, e"
           => ["a","b,c,d","e"]

           jq ´{"k": {"a": 1, "b": 2}} * {"k": {"a": 0,"c": 3}}´
              null
           => {"k": {"a": 0, "b": 2, "c": 3}}

           jq ´.[] | (1 / .)?´
              [1,0,-1]
           => 1, -1

   length
       The builtin function length gets the length of various different types of value:

       ○   The  length of a string is the number of Unicode codepoints it contains (which will be
           the same as its JSON-encoded length in bytes if it´s pure ASCII).

       ○   The length of an array is the number of elements.

       ○   The length of an object is the number of key-value pairs.

       ○   The length of null is zero.

           jq ´.[] | length´ [[1,2], "string", {"a":2}, null] => 2, 6, 1, 0

   utf8bytelength
       The builtin function utf8bytelength outputs the number of bytes used to encode a string in
       UTF-8.

           jq ´utf8bytelength´
              "\u03bc"
           => 2

   keys, keys_unsorted
       The builtin function keys, when given an object, returns its keys in an array.

       The  keys  are  sorted  "alphabetically", by unicode codepoint order. This is not an order
       that makes particular sense in any particular language, but you can count on it being  the
       same for any two objects with the same set of keys, regardless of locale settings.

       When  keys  is  given  an array, it returns the valid indices for that array: the integers
       from 0 to length-1.

       The keys_unsorted function is just like keys, but if the input is an object then the  keys
       will not be sorted, instead the keys will roughly be in insertion order.

           jq ´keys´
              {"abc": 1, "abcd": 2, "Foo": 3}
           => ["Foo", "abc", "abcd"]

           jq ´keys´
              [42,3,35]
           => [0,1,2]

   has(key)
       The  builtin function has returns whether the input object has the given key, or the input
       array has an element at the given index.

       has($key) has the same effect as checking whether $key is a member of the  array  returned
       by keys, although has will be faster.

           jq ´map(has("foo"))´
              [{"foo": 42}, {}]
           => [true, false]

           jq ´map(has(2))´
              [[0,1], ["a","b","c"]]
           => [false, true]

   in
       The  builtin  function  in returns whether or not the input key is in the given object, or
       the input index corresponds to an element in the  given  array.  It  is,  essentially,  an
       inversed version of has.

           jq ´.[] | in({"foo": 42})´
              ["foo", "bar"]
           => true, false

           jq ´map(in([0,1]))´
              [2, 0]
           => [false, true]

   map(x), map_values(x)
       For  any  filter  x,  map(x) will run that filter for each element of the input array, and
       return the outputs in a new array. map(.+1) will increment each element  of  an  array  of
       numbers.

       Similarly,  map_values(x)  will  run  that  filter for each element, but it will return an
       object when an object is passed.

       map(x) is equivalent to [.[]  |  x].  In  fact,  this  is  how  it´s  defined.  Similarly,
       map_values(x) is defined as .[] |= x.

           jq ´map(.+1)´
              [1,2,3]
           => [2,3,4]

           jq ´map_values(.+1)´
              {"a": 1, "b": 2, "c": 3}
           => {"a": 2, "b": 3, "c": 4}

   path(path_expression)
       Outputs array representations of the given path expression in .. The outputs are arrays of
       strings (object keys) and/or numbers (array indices).

       Path expressions are jq expressions like .a, but also .[]. There are  two  types  of  path
       expressions:  ones that can match exactly, and ones that cannot. For example, .a.b.c is an
       exact match path expression, while .a[].b is not.

       path(exact_path_expression) will produce the array representation of the  path  expression
       even if it does not exist in ., if . is null or an array or an object.

       path(pattern)  will  produce  array  representations  of the paths matching pattern if the
       paths exist in ..

       Note that the path expressions are not different from normal expressions.  The  expression
       path(..|select(type=="boolean"))  outputs  all  the paths to boolean values in ., and only
       those paths.

           jq ´path(.a[0].b)´
              null
           => ["a",0,"b"]

           jq ´[path(..)]´
              {"a":[{"b":1}]}
           => [[],["a"],["a",0],["a",0,"b"]]

   del(path_expression)
       The builtin function del removes a key and its corresponding value from an object.

           jq ´del(.foo)´
              {"foo": 42, "bar": 9001, "baz": 42}
           => {"bar": 9001, "baz": 42}

           jq ´del(.[1, 2])´
              ["foo", "bar", "baz"]
           => ["foo"]

   getpath(PATHS)
       The builtin function getpath outputs the values in . found at each path in PATHS.

           jq ´getpath(["a","b"])´
              null
           => null

           jq ´[getpath(["a","b"], ["a","c"])]´
              {"a":{"b":0, "c":1}}
           => [0, 1]

   setpath(PATHS; VALUE)
       The builtin function setpath sets the PATHS in . to VALUE.

           jq ´setpath(["a","b"]; 1)´
              null
           => {"a": {"b": 1}}

           jq ´setpath(["a","b"]; 1)´
              {"a":{"b":0}}
           => {"a": {"b": 1}}

           jq ´setpath([0,"a"]; 1)´
              null
           => [{"a":1}]

   delpaths(PATHS)
       The builtin function delpaths sets the PATHS in .. PATHS must be an array of paths,  where
       each path is an array of strings and numbers.

           jq ´delpaths([["a","b"]])´
              {"a":{"b":1},"x":{"y":2}}
           => {"a":{},"x":{"y":2}}

   to_entries, from_entries, with_entries
       These  functions  convert between an object and an array of key-value pairs. If to_entries
       is passed an object, then for each k: v entry in the  input,  the  output  array  includes
       {"key": k, "value": v}.

       from_entries  does  the  opposite  conversion,  and  with_entries(foo)  is a shorthand for
       to_entries | map(foo) | from_entries, useful for doing some  operation  to  all  keys  and
       values of an object. from_entries accepts key, Key, name, Name, value and Value as keys.

           jq ´to_entries´
              {"a": 1, "b": 2}
           => [{"key":"a", "value":1}, {"key":"b", "value":2}]

           jq ´from_entries´
              [{"key":"a", "value":1}, {"key":"b", "value":2}]
           => {"a": 1, "b": 2}

           jq ´with_entries(.key |= "KEY_" + .)´
              {"a": 1, "b": 2}
           => {"KEY_a": 1, "KEY_b": 2}

   select(boolean_expression)
       The  function select(foo) produces its input unchanged if foo returns true for that input,
       and produces no output otherwise.

       It´s useful for filtering lists: [1,2,3] | map(select(. >= 2)) will give you [2,3].

           jq ´map(select(. >= 2))´
              [1,5,3,0,7]
           => [5,3,7]

           jq ´.[] | select(.id == "second")´
              [{"id": "first", "val": 1}, {"id": "second", "val": 2}]
           => {"id": "second", "val": 2}

   arrays, objects, iterables, booleans,  numbers,  normals,  finites,  strings,  nulls,  values,
       scalars
       These  built-ins  select  only  inputs  that  are  arrays,  objects,  iterables (arrays or
       objects), booleans, numbers, normal  numbers,  finite  numbers,  strings,  null,  non-null
       values, and non-iterables, respectively.

           jq ´.[]|numbers´
              [[],{},1,"foo",null,true,false]
           => 1

   empty
       empty returns no results. None at all. Not even null.

       It´s useful on occasion. You´ll know if you need it :)

           jq ´1, empty, 2´
              null
           => 1, 2

           jq ´[1,2,empty,3]´
              null
           => [1,2,3]

   error(message)
       Produces  an  error, just like .a applied to values other than null and objects would, but
       with the given message as the error´s value. Errors can  be  caught  with  try/catch;  see
       below.

   halt
       Stops the jq program with no further outputs. jq will exit with exit status 0.

   halt_error, halt_error(exit_code)
       Stops  the  jq program with no further outputs. The input will be printed on stderr as raw
       output (i.e., strings will not have double quotes) with no decoration, not even a newline.

       The given exit_code (defaulting to 5) will be jq´s exit status.

       For example, "Error: somthing went wrong\n"|halt_error(1).

   $__loc__
       Produces an object with a "file" key and a "line" key, with the filename and  line  number
       where $__loc__ occurs, as values.

           jq ´try error("\($__loc__)") catch .´
              null
           => "{\"file\":\"<top-level>\",\"line\":1}"

   paths, paths(node_filter), leaf_paths
       paths  outputs  the  paths to all the elements in its input (except it does not output the
       empty list, representing . itself).

       paths(f) outputs the paths to any values for which f  is  true.  That  is,  paths(numbers)
       outputs the paths to all numeric values.

       leaf_paths  is an alias of paths(scalars); leaf_paths is deprecated and will be removed in
       the next major release.

           jq ´[paths]´
              [1,[[],{"a":2}]]
           => [[0],[1],[1,0],[1,1],[1,1,"a"]]

           jq ´[paths(scalars)]´
              [1,[[],{"a":2}]]
           => [[0],[1,1,"a"]]

   add
       The filter add takes as input an array, and produces as output the elements of  the  array
       added  together.  This might mean summed, concatenated or merged depending on the types of
       the elements of the input array - the rules are the same  as  those  for  the  +  operator
       (described above).

       If the input is an empty array, add returns null.

           jq ´add´
              ["a","b","c"]
           => "abc"

           jq ´add´
              [1, 2, 3]
           => 6

           jq ´add´
              []
           => null

   any, any(condition), any(generator; condition)
       The  filter  any takes as input an array of boolean values, and produces true as output if
       any of the elements of the array are true.

       If the input is an empty array, any returns false.

       The any(condition) form applies the given condition to the elements of the input array.

       The any(generator; condition) form applies the given condition to all the outputs  of  the
       given generator.

           jq ´any´
              [true, false]
           => true

           jq ´any´
              [false, false]
           => false

           jq ´any´
              []
           => false

   all, all(condition), all(generator; condition)
       The  filter  all takes as input an array of boolean values, and produces true as output if
       all of the elements of the array are true.

       The all(condition) form applies the given condition to the elements of the input array.

       The all(generator; condition) form applies the given condition to all the outputs  of  the
       given generator.

       If the input is an empty array, all returns true.

           jq ´all´
              [true, false]
           => false

           jq ´all´
              [true, true]
           => true

           jq ´all´
              []
           => true

   flatten, flatten(depth)
       The  filter flatten takes as input an array of nested arrays, and produces a flat array in
       which all arrays inside the original array have been recursively replaced by their values.
       You can pass an argument to it to specify how many levels of nesting to flatten.

       flatten(2) is like flatten, but going only up to two levels deep.

           jq ´flatten´
              [1, [2], [[3]]]
           => [1, 2, 3]

           jq ´flatten(1)´
              [1, [2], [[3]]]
           => [1, 2, [3]]

           jq ´flatten´
              [[]]
           => []

           jq ´flatten´
              [{"foo": "bar"}, [{"foo": "baz"}]]
           => [{"foo": "bar"}, {"foo": "baz"}]

   range(upto), range(from;upto) range(from;upto;by)
       The  range  function  produces  a range of numbers. range(4;10) produces 6 numbers, from 4
       (inclusive) to  10  (exclusive).  The  numbers  are  produced  as  separate  outputs.  Use
       [range(4;10)] to get a range as an array.

       The  one  argument form generates numbers from 0 to the given number, with an increment of
       1.

       The two argument form generates numbers from from to upto with an increment of 1.

       The three argument form generates numbers from to upto with an increment of by.

           jq ´range(2;4)´
              null
           => 2, 3

           jq ´[range(2;4)]´
              null
           => [2,3]

           jq ´[range(4)]´
              null
           => [0,1,2,3]

           jq ´[range(0;10;3)]´
              null
           => [0,3,6,9]

           jq ´[range(0;10;-1)]´
              null
           => []

           jq ´[range(0;-5;-1)]´
              null
           => [0,-1,-2,-3,-4]

   floor
       The floor function returns the floor of its numeric input.

           jq ´floor´
              3.14159
           => 3

   sqrt
       The sqrt function returns the square root of its numeric input.

           jq ´sqrt´
              9
           => 3

   tonumber
       The tonumber function parses its input as a number. It  will  convert  correctly-formatted
       strings  to  their numeric equivalent, leave numbers alone, and give an error on all other
       input.

           jq ´.[] | tonumber´
              [1, "1"]
           => 1, 1

   tostring
       The tostring function prints its input as a string. Strings are left  unchanged,  and  all
       other values are JSON-encoded.

           jq ´.[] | tostring´
              [1, "1", [1]]
           => "1", "1", "[1]"

   type
       The  type  function  returns  the  type of its argument as a string, which is one of null,
       boolean, number, string, array or object.

           jq ´map(type)´
              [0, false, [], {}, null, "hello"]
           => ["number", "boolean", "array", "object", "null", "string"]

   infinite, nan, isinfinite, isnan, isfinite, isnormal
       Some arithmetic operations can yield infinities and  "not  a  number"  (NaN)  values.  The
       isinfinite  builtin  returns true if its input is infinite. The isnan builtin returns true
       if its input is a NaN. The infinite builtin returns a positive  infinite  value.  The  nan
       builtin returns a NaN. The isnormal builtin returns true if its input is a normal number.

       Note that division by zero raises an error.

       Currently most arithmetic operations operating on infinities, NaNs, and sub-normals do not
       raise errors.

           jq ´.[] | (infinite * .) < 0´
              [-1, 1]
           => true, false

           jq ´infinite, nan | type´
              null
           => "number", "number"

   sort, sort_by(path_expression)
       The sort functions sorts its input, which must be an  array.  Values  are  sorted  in  the
       following order:

       ○   nullfalsetrue

       ○   numbers

       ○   strings, in alphabetical order (by unicode codepoint value)

       ○   arrays, in lexical order

       ○   objects

       The  ordering  for  objects is a little complex: first they´re compared by comparing their
       sets of keys (as arrays in sorted order), and if their keys are equal then the values  are
       compared key by key.

       sort may be used to sort by a particular field of an object, or by applying any jq filter.

       sort_by(foo) compares two elements by comparing the result of foo on each element.

           jq ´sort´
              [8,3,null,6]
           => [null,3,6,8]

           jq ´sort_by(.foo)´
              [{"foo":4, "bar":10}, {"foo":3, "bar":100}, {"foo":2, "bar":1}]
           => [{"foo":2, "bar":1}, {"foo":3, "bar":100}, {"foo":4, "bar":10}]

   group_by(path_expression)
       group_by(.foo)  takes  as  input  an array, groups the elements having the same .foo field
       into separate arrays, and produces all of these arrays as  elements  of  a  larger  array,
       sorted by the value of the .foo field.

       Any  jq  expression,  not  just  a field access, may be used in place of .foo. The sorting
       order is the same as described in the sort function above.

           jq ´group_by(.foo)´
              [{"foo":1, "bar":10}, {"foo":3, "bar":100}, {"foo":1, "bar":1}]
           => [[{"foo":1, "bar":10}, {"foo":1, "bar":1}], [{"foo":3, "bar":100}]]

   min, max, min_by(path_exp), max_by(path_exp)
       Find the minimum or maximum element of the input array.

       The min_by(path_exp) and max_by(path_exp) functions allow  you  to  specify  a  particular
       field  or  property  to  examine, e.g. min_by(.foo) finds the object with the smallest foo
       field.

           jq ´min´
              [5,4,2,7]
           => 2

           jq ´max_by(.foo)´
              [{"foo":1, "bar":14}, {"foo":2, "bar":3}]
           => {"foo":2, "bar":3}

   unique, unique_by(path_exp)
       The unique function takes as input an array and produces an array of the same elements, in
       sorted order, with duplicates removed.

       The  unique_by(path_exp)  function  will  keep only one element for each value obtained by
       applying the argument. Think of it as making an array by taking one element out  of  every
       group produced by group.

           jq ´unique´
              [1,2,5,3,5,3,1,3]
           => [1,2,3,5]

           jq ´unique_by(.foo)´
              [{"foo": 1, "bar": 2}, {"foo": 1, "bar": 3}, {"foo": 4, "bar": 5}]
           => [{"foo": 1, "bar": 2}, {"foo": 4, "bar": 5}]

           jq ´unique_by(length)´
              ["chunky", "bacon", "kitten", "cicada", "asparagus"]
           => ["bacon", "chunky", "asparagus"]

   reverse
       This function reverses an array.

           jq ´reverse´
              [1,2,3,4]
           => [4,3,2,1]

   contains(element)
       The  filter contains(b) will produce true if b is completely contained within the input. A
       string B is contained in a string A if B is a substring of A. An array B is  contained  in
       an  array  A  if  all  elements  in  B  are  contained in any element in A. An object B is
       contained in object A if all of the values in B are contained in the value in A  with  the
       same key. All other types are assumed to be contained in each other if they are equal.

           jq ´contains("bar")´
              "foobar"
           => true

           jq ´contains(["baz", "bar"])´
              ["foobar", "foobaz", "blarp"]
           => true

           jq ´contains(["bazzzzz", "bar"])´
              ["foobar", "foobaz", "blarp"]
           => false

           jq ´contains({foo: 12, bar: [{barp: 12}]})´
              {"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}
           => true

           jq ´contains({foo: 12, bar: [{barp: 15}]})´
              {"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}
           => false

   indices(s)
       Outputs an array containing the indices in . where s occurs. The input may be an array, in
       which case if s is an array then the indices output will be those where all elements in  .
       match those of s.

           jq ´indices(", ")´
              "a,b, cd, efg, hijk"
           => [3,7,12]

           jq ´indices(1)´
              [0,1,2,1,3,1,4]
           => [1,3,5]

           jq ´indices([1,2])´
              [0,1,2,3,1,4,2,5,1,2,6,7]
           => [1,8]

   index(s), rindex(s)
       Outputs the index of the first (index) or last (rindex) occurrence of s in the input.

           jq ´index(", ")´
              "a,b, cd, efg, hijk"
           => 3

           jq ´rindex(", ")´
              "a,b, cd, efg, hijk"
           => 12

   inside
       The  filter  inside(b) will produce true if the input is completely contained within b. It
       is, essentially, an inversed version of contains.

           jq ´inside("foobar")´
              "bar"
           => true

           jq ´inside(["foobar", "foobaz", "blarp"])´
              ["baz", "bar"]
           => true

           jq ´inside(["foobar", "foobaz", "blarp"])´
              ["bazzzzz", "bar"]
           => false

           jq ´inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})´
              {"foo": 12, "bar": [{"barp": 12}]}
           => true

           jq ´inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})´
              {"foo": 12, "bar": [{"barp": 15}]}
           => false

   startswith(str)
       Outputs true if . starts with the given string argument.

           jq ´[.[]|startswith("foo")]´
              ["fo", "foo", "barfoo", "foobar", "barfoob"]
           => [false, true, false, true, false]

   endswith(str)
       Outputs true if . ends with the given string argument.

           jq ´[.[]|endswith("foo")]´
              ["foobar", "barfoo"]
           => [false, true]

   combinations, combinations(n)
       Outputs all combinations of the elements of the arrays in the input  array.  If  given  an
       argument n, it outputs all combinations of n repetitions of the input array.

           jq ´combinations´
              [[1,2], [3, 4]]
           => [1, 3], [1, 4], [2, 3], [2, 4]

           jq ´combinations(2)´
              [0, 1]
           => [0, 0], [0, 1], [1, 0], [1, 1]

   ltrimstr(str)
       Outputs its input with the given prefix string removed, if it starts with it.

           jq ´[.[]|ltrimstr("foo")]´
              ["fo", "foo", "barfoo", "foobar", "afoo"]
           => ["fo","","barfoo","bar","afoo"]

   rtrimstr(str)
       Outputs its input with the given suffix string removed, if it ends with it.

           jq ´[.[]|rtrimstr("foo")]´
              ["fo", "foo", "barfoo", "foobar", "foob"]
           => ["fo","","bar","foobar","foob"]

   explode
       Converts an input string into an array of the string´s codepoint numbers.

           jq ´explode´
              "foobar"
           => [102,111,111,98,97,114]

   implode
       The inverse of explode.

           jq ´implode´
              [65, 66, 67]
           => "ABC"

   split(str)
       Splits an input string on the separator argument.

           jq ´split(", ")´
              "a, b,c,d, e, "
           => ["a","b,c,d","e",""]

   join(str)
       Joins  the  array  of  elements given as input, using the argument as separator. It is the
       inverse of split: that is, running  split("foo")  |  join("foo")  over  any  input  string
       returns said input string.

       Numbers  and  booleans  in  the input are converted to strings. Null values are treated as
       empty strings. Arrays and objects in the input are not supported.

           jq ´join(", ")´
              ["a","b,c,d","e"]
           => "a, b,c,d, e"

           jq ´join(" ")´
              ["a",1,2.3,true,null,false]
           => "a 1 2.3 true  false"

   ascii_downcase, ascii_upcase
       Emit a copy of the input string with its alphabetic characters (a-z and A-Z) converted  to
       the specified case.

   while(cond; update)
       The  while(cond; update) function allows you to repeatedly apply an update to . until cond
       is false.

       Note that while(cond; update) is internally defined as a recursive jq function.  Recursive
       calls  within  while  will  not  consume  additional memory if update produces at most one
       output for each input. See advanced topics below.

           jq ´[while(.<100; .*2)]´
              1
           => [1,2,4,8,16,32,64]

   until(cond; next)
       The until(cond; next) function  allows  you  to  repeatedly  apply  the  expression  next,
       initially  to  . then to its own output, until cond is true. For example, this can be used
       to implement a factorial function (see below).

       Note that until(cond; next) is internally defined as a recursive  jq  function.  Recursive
       calls  within  until()  will  not  consume  additional memory if next produces at most one
       output for each input. See advanced topics below.

           jq ´[.,1]|until(.[0] < 1; [.[0] - 1, .[1] * .[0]])|.[1]´
              4
           => 24

   recurse(f), recurse, recurse(f; condition), recurse_down
       The recurse(f) function allows you to search through a recursive  structure,  and  extract
       interesting data from all levels. Suppose your input represents a filesystem:

           {"name": "/", "children": [
             {"name": "/bin", "children": [
               {"name": "/bin/ls", "children": []},
               {"name": "/bin/sh", "children": []}]},
             {"name": "/home", "children": [
               {"name": "/home/stephen", "children": [
                 {"name": "/home/stephen/jq", "children": []}]}]}]}

       Now  suppose you want to extract all of the filenames present. You need to retrieve .name,
       .children[].name, .children[].children[].name, and so on. You can do this with:

           recurse(.children[]) | .name

       When called without an argument, recurse is equivalent to recurse(.[]?).

       recurse(f) is identical to recurse(f; . != null) and can be used  without  concerns  about
       recursion depth.

       recurse(f;  condition)  is  a  generator which begins by emitting . and then emits in turn
       .|f, .|f|f, .|f|f|f, ... so long as  the  computed  value  satisfies  the  condition.  For
       example, to generate all the integers, at least in principle, one could write recurse(.+1;
       true).

       For legacy reasons, recurse_down exists as an alias to calling recurse without  arguments.
       This alias is considered deprecated and will be removed in the next major release.

       The  recursive  calls in recurse will not consume additional memory whenever f produces at
       most a single output for each input.

           jq ´recurse(.foo[])´
              {"foo":[{"foo": []}, {"foo":[{"foo":[]}]}]}
           => {"foo":[{"foo":[]},{"foo":[{"foo":[]}]}]}, {"foo":[]}, {"foo":[{"foo":[]}]}, {"foo":[]}

           jq ´recurse´
              {"a":0,"b":[1]}
           => {"a":0,"b":[1]}, 0, [1], 1

           jq ´recurse(. * .; . < 20)´
              2
           => 2, 4, 16

   walk(f)
       The walk(f) function applies f recursively to every component of the input entity. When an
       array  is  encountered,  f  is first applied to its elements and then to the array itself;
       when an object is encountered, f is first applied to  all  the  values  and  then  to  the
       object.  In  practice,  f  will  usually test the type of its input, as illustrated in the
       following examples. The first example highlights the usefulness of processing the elements
       of an array of arrays before processing the array itself. The second example shows how all
       the keys of all the objects within the input can be considered for alteration.

           jq ´walk(if type == "array" then sort else . end)´
              [[4, 1, 7], [8, 5, 2], [3, 6, 9]]
           => [[1,4,7],[2,5,8],[3,6,9]]

           jq ´walk( if type == "object" then with_entries( .key |= sub( "^_+"; "") ) else . end )´
              [ { "_a": { "__b": 2 } } ]
           => [{"a":{"b":2}}]

   $ENV, env
       $ENV is an object representing the environment  variables  as  set  when  the  jq  program
       started.

       env outputs an object representing jq´s current environment.

       At the moment there is no builtin for setting environment variables.

           jq ´$ENV.PAGER´
              null
           => "less"

           jq ´env.PAGER´
              null
           => "less"

   transpose
       Transpose a possibly jagged matrix (an array of arrays). Rows are padded with nulls so the
       result is always rectangular.

           jq ´transpose´
              [[1], [2,3]]
           => [[1,2],[null,3]]

   bsearch(x)
       bsearch(x) conducts a binary search for x in the input array. If the input is  sorted  and
       contains x, then bsearch(x) will return its index in the array; otherwise, if the array is
       sorted, it will return (-1 - ix) where ix is an insertion point such that the array  would
       still  be  sorted  after  the insertion of x at ix. If the array is not sorted, bsearch(x)
       will return an integer that is probably of no interest.

           jq ´bsearch(0)´
              [0,1]
           => 0

           jq ´bsearch(0)´
              [1,2,3]
           => -1

           jq ´bsearch(4) as $ix | if $ix < 0 then .[-(1+$ix)] = 4 else . end´
              [1,2,3]
           => [1,2,3,4]

   String interpolation - \(foo)
       Inside a string, you can put an expression inside parens after a backslash.  Whatever  the
       expression returns will be interpolated into the string.

           jq ´"The input was \(.), which is one less than \(.+1)"´
              42
           => "The input was 42, which is one less than 43"

   Convert to/from JSON
       The  tojson  and  fromjson  builtins  dump  values  as JSON texts or parse JSON texts into
       values, respectively. The tojson builtin differs from tostring in  that  tostring  returns
       strings unmodified, while tojson encodes strings as JSON strings.

           jq ´[.[]|tostring]´
              [1, "foo", ["foo"]]
           => ["1","foo","[\"foo\"]"]

           jq ´[.[]|tojson]´
              [1, "foo", ["foo"]]
           => ["1","\"foo\"","[\"foo\"]"]

           jq ´[.[]|tojson|fromjson]´
              [1, "foo", ["foo"]]
           => [1,"foo",["foo"]]

   Format strings and escaping
       The  @foo  syntax is used to format and escape strings, which is useful for building URLs,
       documents in a language like HTML or XML, and so forth. @foo can be used as  a  filter  on
       its own, the possible escapings are:

       @text:

       @json:

       @html:

       @uri:

       @csv:

       @tsv:

       @sh:

       @base64:

       @base64d:

       This  syntax  can  be combined with string interpolation in a useful way. You can follow a
       @foo token with a string literal. The contents of the string literal will not be  escaped.
       However, all interpolations made inside that string literal will be escaped. For instance,

           @uri "https://www.google.com/search?q=\(.search)"

       will produce the following output for the input {"search":"what is jq?"}:

           "https://www.google.com/search?q=what%20is%20jq%3F"

       Note  that  the slashes, question mark, etc. in the URL are not escaped, as they were part
       of the string literal.

           jq ´@html´
              "This works if x < y"
           => "This works if x &lt; y"

           jq ´@sh "echo \(.)"´
              "O´Hara´s Ale"
           => "echo ´O´\\´´Hara´\\´´s Ale´"

           jq ´@base64´
              "This is a message"
           => "VGhpcyBpcyBhIG1lc3NhZ2U="

           jq ´@base64d´
              "VGhpcyBpcyBhIG1lc3NhZ2U="
           => "This is a message"

   Dates
       jq provides some basic date handling functionality, with  some  high-level  and  low-level
       builtins. In all cases these builtins deal exclusively with time in UTC.

       The fromdateiso8601 builtin parses datetimes in the ISO 8601 format to a number of seconds
       since the Unix epoch (1970-01-01T00:00:00Z). The todateiso8601 builtin does the inverse.

       The fromdate builtin parses datetime strings. Currently fromdate only  supports  ISO  8601
       datetime  strings,  but  in  the  future it will attempt to parse datetime strings in more
       formats.

       The todate builtin is an alias for todateiso8601.

       The now builtin outputs the current time, in seconds since the Unix epoch.

       Low-level jq interfaces to the C-library  time  functions  are  also  provided:  strptime,
       strftime,  strflocaltime,  mktime,  gmtime,  and  localtime.  Refer to your host operating
       system´s documentation for the format strings used by strptime and strftime.  Note:  these
       are  not  necessarily  stable  interfaces  in  jq,  particularly  as to their localization
       functionality.

       The gmtime builtin consumes a number of seconds since the Unix epoch and outputs a "broken
       down  time" representation of Greenwhich Meridian time as an array of numbers representing
       (in this order): the year, the month (zero-based), the day of the month  (one-based),  the
       hour  of  the  day, the minute of the hour, the second of the minute, the day of the week,
       and the day of the year -- all one-based unless otherwise stated.  The  day  of  the  week
       number  may be wrong on some systems for dates before March 1st 1900, or after December 31
       2099.

       The localtime builtin works like the gmtime builtin, but using the local timezone setting.

       The mktime builtin consumes "broken down time" representations of time  output  by  gmtime
       and strptime.

       The strptime(fmt) builtin parses input strings matching the fmt argument. The output is in
       the "broken down time" representation consumed by gmtime and output by mktime.

       The strftime(fmt) builtin formats a time (GMT) with the given  format.  The  strflocaltime
       does the same, but using the local timezone setting.

       The  format  strings  for  strptime  and  strftime  are  described  in  typical  C library
       documentation. The format string for ISO 8601 datetime is "%Y-%m-%dT%H:%M:%SZ".

       jq may not support some or all of this date functionality on some systems. In  particular,
       the %u and %j specifiers for strptime(fmt) are not supported on macOS.

           jq ´fromdate´
              "2015-03-05T23:51:47Z"
           => 1425599507

           jq ´strptime("%Y-%m-%dT%H:%M:%SZ")´
              "2015-03-05T23:51:47Z"
           => [2015,2,5,23,51,47,4,63]

           jq ´strptime("%Y-%m-%dT%H:%M:%SZ")|mktime´
              "2015-03-05T23:51:47Z"
           => 1425599507

   SQL-Style Operators
       jq provides a few SQL-style operators.

       INDEX(stream; index_expression):

       JOIN($idx; stream; idx_expr; join_expr):

       JOIN($idx; stream; idx_expr):

       JOIN($idx; idx_expr):

       IN(s):

       IN(source; s):

   builtins
       Returns a list of all builtin functions in the format name/arity. Since functions with the
       same name but different arities are considered separate functions, all/0, all/1, and all/2
       would all be present in the list.

CONDITIONALS AND COMPARISONS

   ==, !=
       The  expression  ´a == b´ will produce ´true´ if the result of a and b are equal (that is,
       if they represent equivalent JSON documents) and ´false´ otherwise. In particular, strings
       are  never  considered equal to numbers. If you´re coming from Javascript, jq´s == is like
       Javascript´s === - considering values equal only when they have the same type as  well  as
       the same value.

       != is "not equal", and ´a != b´ returns the opposite value of ´a == b´

           jq ´.[] == 1´
              [1, 1.0, "1", "banana"]
           => true, true, false, false

   if-then-else
       if  A  then  B else C end will act the same as B if A produces a value other than false or
       null, but act the same as C otherwise.

       Checking for false or null is a simpler notion of "truthiness" than is found in Javascript
       or Python, but it means that you´ll sometimes have to be more explicit about the condition
       you want: you can´t test whether, e.g. a string is empty using if .name then A else B end,
       you´ll need something more like if (.name | length) > 0 then A else B end instead.

       If  the  condition  A  produces multiple results, then B is evaluated once for each result
       that is not false or null, and C is evaluated once for each false or null.

       More cases can be added to an if using elif A then B syntax.

           jq ´if . == 0 then

       "zero" elif . == 1 then "one" else "many" end´ 2 => "many"

   >, >=, <=, <
       The comparison operators >, >=, <=, < return whether their left argument is greater  than,
       greater  than  or  equal  to,  less  than  or  equal  to or less than their right argument
       (respectively).

       The ordering is the same as that described for sort, above.

           jq ´. < 5´
              2
           => true

   and/or/not
       jq supports the normal Boolean operators and/or/not. They have the same standard of  truth
       as  if  expressions - false and null are considered "false values", and anything else is a
       "true value".

       If an operand of one of these operators produces multiple  results,  the  operator  itself
       will produce a result for each input.

       not  is in fact a builtin function rather than an operator, so it is called as a filter to
       which things can be piped rather than with special syntax, as in .foo and .bar | not.

       These three only produce the values "true" and "false", and so are only useful for genuine
       Boolean    operations,    rather    than    the    common    Perl/Python/Ruby   idiom   of
       "value_that_may_be_null or default". If you want to use this form of "or", picking between
       two values rather than evaluating a condition, see the "//" operator below.

           jq ´42 and "a string"´
              null
           => true

           jq ´(true, false) or false´
              null
           => true, false

           jq ´(true, true) and (true, false)´
              null
           => true, false, true, false

           jq ´[true, false | not]´
              null
           => [false, true]

   Alternative operator: //
       A  filter  of  the form a // b produces the same results as a, if a produces results other
       than false and null. Otherwise, a // b produces the same results as b.

       This is useful for providing defaults: .foo // 1 will evaluate to 1  if  there´s  no  .foo
       element in the input. It´s similar to how or is sometimes used in Python (jq´s or operator
       is reserved for strictly Boolean operations).

           jq ´.foo // 42´
              {"foo": 19}
           => 19

           jq ´.foo // 42´
              {}
           => 42

   try-catch
       Errors can be caught by using try EXP catch EXP. The first expression is executed, and  if
       it fails then the second is executed with the error message. The output of the handler, if
       any, is output as if it had been the output of the expression to try.

       The try EXP form uses empty as the exception handler.

           jq ´try .a catch ". is not an object"´
              true
           => ". is not an object"

           jq ´[.[]|try .a]´
              [{}, true, {"a":1}]
           => [null, 1]

           jq ´try error("some exception") catch .´
              true
           => "some exception"

   Breaking out of control structures
       A convenient use of try/catch is to break out of control structures like reduce,  foreach,
       while, and so on.

       For example:

           # Repeat an expression until it raises "break" as an
           # error, then stop repeating without re-raising the error.
           # But if the error caught is not "break" then re-raise it.
           try repeat(exp) catch .=="break" then empty else error;

       jq has a syntax for named lexical labels to "break" or "go (back) to":

           label $out | ... break $out ...

       The  break  $label_name  expression will cause the program to to act as though the nearest
       (to the left) label $label_name produced empty.

       The relationship between the break and corresponding label is lexical: the label has to be
       "visible" from the break.

       To break out of a reduce, for example:

           label $out | reduce .[] as $item (null; if .==false then break $out else ... end)

       The following jq program produces a syntax error:

           break $out

       because no label $out is visible.

   Error Suppression / Optional Operator: ?
       The ? operator, used as EXP?, is shorthand for try EXP.

           jq ´[.[]|(.a)?]´
              [{}, true, {"a":1}]
           => [null, 1]

REGULAR EXPRESSIONS (PCRE)

       jq uses the Oniguruma regular expression library, as do php, ruby, TextMate, Sublime Text,
       etc, so the description here will focus on jq specifics.

       The jq regex filters are defined so that they can be used using one of these patterns:

           STRING | FILTER( REGEX )
           STRING | FILTER( REGEX; FLAGS )
           STRING | FILTER( [REGEX] )
           STRING | FILTER( [REGEX, FLAGS] )

       where: * STRING, REGEX and FLAGS are jq strings and subject to jq string interpolation;  *
       REGEX,  after string interpolation, should be a valid PCRE regex; * FILTER is one of test,
       match, or capture, as described below.

       FLAGS is a string consisting of one of more of the supported flags:

       ○   g - Global search (find all matches, not just the first)

       ○   i - Case insensitive search

       ○   m - Multi line mode (´.´ will match newlines)

       ○   n - Ignore empty matches

       ○   p - Both s and m modes are enabled

       ○   s - Single line mode (´^´ -> ´\A´, ´$´ -> ´\Z´)

       ○   l - Find longest possible matches

       ○   x - Extended regex format (ignore whitespace and comments)

       To match whitespace in an x pattern use an escape such as \s, e.g.

       ○   test( "a\sb", "x" ).

       Note that certain flags may also be specified within REGEX, e.g.

       ○   jq -n ´("test", "TEst", "teST", "TEST") | test( "(?i)te(?-i)st" )´

       evaluates to: true, true, false, false.

   test(val), test(regex; flags)
       Like match, but does not return match objects, only true or false for whether or  not  the
       regex matches the input.

           jq ´test("foo")´
              "foo"
           => true

           jq ´.[] | test("a b c # spaces are ignored"; "ix")´
              ["xabcd", "ABC"]
           => true, true

   match(val), match(regex; flags)
       match outputs an object for each match it finds. Matches have the following fields:

       ○   offset - offset in UTF-8 codepoints from the beginning of the input

       ○   length - length in UTF-8 codepoints of the match

       ○   string - the string that it matched

       ○   captures - an array of objects representing capturing groups.

       Capturing group objects have the following fields:

       ○   offset - offset in UTF-8 codepoints from the beginning of the input

       ○   length - length in UTF-8 codepoints of this capturing group

       ○   string - the string that was captured

       ○   name - the name of the capturing group (or null if it was unnamed)

       Capturing groups that did not match anything return an offset of -1

           jq ´match("(abc)+"; "g")´
              "abc abc"
           => {"offset": 0, "length": 3, "string": "abc", "captures": [{"offset": 0, "length": 3, "string": "abc", "name": null}]}, {"offset": 4, "length": 3, "string": "abc", "captures": [{"offset": 4, "length": 3, "string": "abc", "name": null}]}

           jq ´match("foo")´
              "foo bar foo"
           => {"offset": 0, "length": 3, "string": "foo", "captures": []}

           jq ´match(["foo", "ig"])´
              "foo bar FOO"
           => {"offset": 0, "length": 3, "string": "foo", "captures": []}, {"offset": 8, "length": 3, "string": "FOO", "captures": []}

           jq ´match("foo (?<bar123>bar)? foo"; "ig")´
              "foo bar foo foo  foo"
           => {"offset": 0, "length": 11, "string": "foo bar foo", "captures": [{"offset": 4, "length": 3, "string": "bar", "name": "bar123"}]}, {"offset": 12, "length": 8, "string": "foo  foo", "captures": [{"offset": -1, "length": 0, "string": null, "name": "bar123"}]}

           jq ´[ match("."; "g")] | length´
              "abc"
           => 3

   capture(val), capture(regex; flags)
       Collects  the  named  captures in a JSON object, with the name of each capture as the key,
       and the matched string as the corresponding value.

           jq ´capture("(?<a>[a-z]+)-(?<n>[0-9]+)")´
              "xyzzy-14"
           => { "a": "xyzzy", "n": "14" }

   scan(regex), scan(regex; flags)
       Emit a stream of the non-overlapping substrings of the  input  that  match  the  regex  in
       accordance with the flags, if any have been specified. If there is no match, the stream is
       empty. To capture all the matches for each input string, use the idiom [ expr  ],  e.g.  [
       scan(regex) ].

   split(regex; flags)
       For backwards compatibility, split splits on a string, not a regex.

   splits(regex), splits(regex; flags)
       These  provide the same results as their split counterparts, but as a stream instead of an
       array.

   sub(regex; tostring) sub(regex; string; flags)
       Emit the string obtained by replacing the first match of regex in the  input  string  with
       tostring,  after interpolation. tostring should be a jq string, and may contain references
       to named captures. The named captures are, in effect,  presented  as  a  JSON  object  (as
       constructed by capture) to tostring, so a reference to a captured variable named "x" would
       take the form: "(.x)".

   gsub(regex; string), gsub(regex; string; flags)
       gsub is like sub but all the non-overlapping occurrences of the regex are replaced by  the
       string, after interpolation.

ADVANCED FEATURES

       Variables  are  an absolute necessity in most programming languages, but they´re relegated
       to an "advanced feature" in jq.

       In most languages, variables are the only means of passing around data. If you calculate a
       value,  and  you  want to use it more than once, you´ll need to store it in a variable. To
       pass a value to another part of the program, you´ll need  that  part  of  the  program  to
       define  a variable (as a function parameter, object member, or whatever) in which to place
       the data.

       It is also possible to define functions in jq, although this is is a feature whose biggest
       use  is defining jq´s standard library (many jq functions such as map and find are in fact
       written in jq).

       jq has reduction operators, which are very powerful but a bit  tricky.  Again,  these  are
       mostly used internally, to define some useful bits of jq´s standard library.

       It  may  not  be  obvious at first, but jq is all about generators (yes, as often found in
       other languages). Some utilities are provided to help deal with generators.

       Some minimal I/O support (besides reading JSON from standard input, and  writing  JSON  to
       standard output) is available.

       Finally, there is a module/library system.

   Variable / Symbolic Binding Operator: ... as $identifier | ...
       In  jq,  all  filters  have an input and an output, so manual plumbing is not necessary to
       pass a value from one part of a program to the next. Many expressions, for instance a + b,
       pass  their  input  to  two distinct subexpressions (here a and b are both passed the same
       input), so variables aren´t usually necessary in order to use a value twice.

       For instance, calculating the average  value  of  an  array  of  numbers  requires  a  few
       variables in most languages - at least one to hold the array, perhaps one for each element
       or for a loop counter. In jq, it´s simply add / length - the add expression is  given  the
       array  and produces its sum, and the length expression is given the array and produces its
       length.

       So, there´s generally a cleaner way to solve most problems in jq than defining  variables.
       Still,  sometimes  they  do  make  things  easier,  so  jq lets you define variables using
       expression as $variable. All variable names start with $. Here´s a slightly uglier version
       of the array-averaging example:

           length as $array_length | add / $array_length

       We´ll  need  a more complicated problem to find a situation where using variables actually
       makes our lives easier.

       Suppose we have an array of blog posts, with "author"  and  "title"  fields,  and  another
       object which is used to map author usernames to real names. Our input looks like:

           {"posts": [{"title": "Frist psot", "author": "anon"},
                      {"title": "A well-written article", "author": "person1"}],
            "realnames": {"anon": "Anonymous Coward",
                          "person1": "Person McPherson"}}

       We want to produce the posts with the author field containing a real name, as in:

           {"title": "Frist psot", "author": "Anonymous Coward"}
           {"title": "A well-written article", "author": "Person McPherson"}

       We use a variable, $names, to store the realnames object, so that we can refer to it later
       when looking up author usernames:

           .realnames as $names | .posts[] | {title, author: $names[.author]}

       The expression exp as $x | ... means: for each value of expression exp, run  the  rest  of
       the  pipeline  with  the  entire  original  input,  and with $x set to that value. Thus as
       functions as something of a foreach loop.

       Just as {foo} is a handy way of writing {foo: .foo}, so {$foo} is a handy way  of  writing
       {foo:$foo}.

       Multiple  variables  may  be  declared using a single as expression by providing a pattern
       that matches the structure of the input (this is known as "destructuring"):

           . as {realnames: $names, posts: [$first, $second]} | ...

       The variable declarations in array patterns (e.g., . as [$first,  $second])  bind  to  the
       elements  of the array in from the element at index zero on up, in order. When there is no
       value at the index for an array pattern element, null is bound to that variable.

       Variables are scoped over the rest of the expression that defines them, so

           .realnames as $names | (.posts[] | {title, author: $names[.author]})

       will work, but

           (.realnames as $names | .posts[]) | {title, author: $names[.author]}

       won´t.

       For programming language theorists, it´s more  accurate  to  say  that  jq  variables  are
       lexically-scoped  bindings. In particular there´s no way to change the value of a binding;
       one can only setup a new binding with the same name, but which will not be  visible  where
       the old one was.

           jq ´.bar as $x | .foo | . + $x´
              {"foo":10, "bar":200}
           => 210

           jq ´. as $i|[(.*2|. as $i| $i), $i]´
              5
           => [10,5]

           jq ´. as [$a, $b, {c: $c}] | $a + $b + $c´
              [2, 3, {"c": 4, "d": 5}]
           => 9

           jq ´.[] as [$a, $b] | {a: $a, b: $b}´
              [[0], [0, 1], [2, 1, 0]]
           => {"a":0,"b":null}, {"a":0,"b":1}, {"a":2,"b":1}

   Destructuring Alternative Operator: ?//
       The  destructuring  alternative operator provides a concise mechanism for destructuring an
       input that can take one of several forms.

       Suppose we have an API that returns a list of resources and events associated  with  them,
       and we want to get the user_id and timestamp of the first event for each resource. The API
       (having been clumsily converted from XML) will only wrap the events in  an  array  if  the
       resource has multiple events:

           {"resources": [{"id": 1, "kind": "widget", "events": {"action": "create", "user_id": 1, "ts": 13}},
                          {"id": 2, "kind": "widget", "events": [{"action": "create", "user_id": 1, "ts": 14}, {"action": "destroy", "user_id": 1, "ts": 15}]}]}

       We can use the destructuring alternative operator to handle this structural change simply:

           .resources[] as {$id, $kind, events: {$user_id, $ts}} ?// {$id, $kind, events: [{$user_id, $ts}]} | {$user_id, $kind, $id, $ts}

       Or, if we aren´t sure if the input is an array of values or an object:

           .[] as [$id, $kind, $user_id, $ts] ?// {$id, $kind, $user_id, $ts} | ...

       Each  alternative  need not define all of the same variables, but all named variables will
       be available to the subsequent expression. Variables not matched in the  alternative  that
       succeeded will be null:

           .resources[] as {$id, $kind, events: {$user_id, $ts}} ?// {$id, $kind, events: [{$first_user_id, $first_ts}]} | {$user_id, $first_user_id, $kind, $id, $ts, $first_ts}

       Additionally, if the subsequent expression returns an error, the alternative operator will
       attempt to try the next binding. Errors that occur during the final alternative are passed
       through.

           [[3]] | .[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end

           jq ´.[] as {$a, $b, c: {$d, $e}} ?// {$a, $b, c: [{$d, $e}]} | {$a, $b, $d, $e}´
              [{"a": 1, "b": 2, "c": {"d": 3, "e": 4}}, {"a": 1, "b": 2, "c": [{"d": 3, "e": 4}]}]
           => {"a":1,"b":2,"d":3,"e":4}, {"a":1,"b":2,"d":3,"e":4}

           jq ´.[] as {$a, $b, c: {$d}} ?// {$a, $b, c: [{$e}]} | {$a, $b, $d, $e}´
              [{"a": 1, "b": 2, "c": {"d": 3, "e": 4}}, {"a": 1, "b": 2, "c": [{"d": 3, "e": 4}]}]
           => {"a":1,"b":2,"d":3,"e":null}, {"a":1,"b":2,"d":null,"e":4}

           jq ´.[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end´
              [[3]]
           => {"a":null,"b":3}

   Defining Functions
       You can give a filter a name using "def" syntax:

           def increment: . + 1;

       From  then on, increment is usable as a filter just like a builtin function (in fact, this
       is how many of the builtins are defined). A function may take arguments:

           def map(f): [.[] | f];

       Arguments are passed as filters (functions with no arguments), not  as  values.  The  same
       argument  may  be  referenced multiple times with different inputs (here f is run for each
       element of the input array). Arguments to a function work more like  callbacks  than  like
       value arguments. This is important to understand. Consider:

           def foo(f): f|f;
           5|foo(.*2)

       The  result will be 20 because f is .*2, and during the first invocation of f . will be 5,
       and the second time it will be 10 (5 * 2), so the result will be  20.  Function  arguments
       are filters, and filters expect an input when invoked.

       If you want the value-argument behaviour for defining simple functions, you can just use a
       variable:

           def addvalue(f): f as $f | map(. + $f);

       Or use the short-hand:

           def addvalue($f): ...;

       With either definition, addvalue(.foo) will add the current input´s  .foo  field  to  each
       element  of  the array. Do note that calling addvalue(.[]) will cause the map(. + $f) part
       to be evaluated once per value in the value of . at the call site.

       Multiple definitions using the same function name are allowed. Each re-definition replaces
       the  previous  one for the same number of function arguments, but only for references from
       functions (or main program) subsequent to the re-definition. See also the section below on
       scoping.

           jq ´def addvalue(f): . + [f]; map(addvalue(.[0]))´
              [[1,2],[10,20]]
           => [[1,2,1], [10,20,10]]

           jq ´def addvalue(f): f as $x | map(. + $x); addvalue(.[0])´
              [[1,2],[10,20]]
           => [[1,2,1,2], [10,20,1,2]]

   Scoping
       There are two types of symbols in jq: value bindings (a.k.a., "variables"), and functions.
       Both are scoped lexically, with expressions being able to refer only to symbols that  have
       been  defined "to the left" of them. The only exception to this rule is that functions can
       refer to themselves so as to be able to create recursive functions.

       For example, in the following expression there is a  binding  which  is  visible  "to  the
       right" of it, ... | .*3 as $times_three | [. + $times_three] | ..., but not "to the left".
       Consider this expression now, ... | (.*3 as $times_three | [.+ $times_three]) | ...:  here
       the binding $times_three is not visible past the closing parenthesis.

   Reduce
       The  reduce  syntax  in  jq  allows  you to combine all of the results of an expression by
       accumulating them into a single  answer.  As  an  example,  we´ll  pass  [3,2,1]  to  this
       expression:

           reduce .[] as $item (0; . + $item)

       For  each  result  that  .[]  produces,  .  +  $item is run to accumulate a running total,
       starting from 0. In this example, .[] produces the results 3, 2, and 1, so the  effect  is
       similar to running something like this:

           0 | (3 as $item | . + $item) |
               (2 as $item | . + $item) |
               (1 as $item | . + $item)

           jq ´reduce .[] as $item (0; . + $item)´
              [10,2,5,3]
           => 20

   isempty(exp)
       Returns true if exp produces no outputs, false otherwise.

           jq ´isempty(empty)´
              null
           => true

   limit(n; exp)
       The limit function extracts up to n outputs from exp.

           jq ´[limit(3;.[])]´
              [0,1,2,3,4,5,6,7,8,9]
           => [0,1,2]

   first(expr), last(expr), nth(n; expr)
       The  first(expr)  and  last(expr)  functions  extract the first and last values from expr,
       respectively.

       The nth(n; expr) function extracts the nth value output by expr. This can  be  defined  as
       def  nth(n;  expr):  last(limit(n  +  1;  expr));.  Note that nth(n; expr) doesn´t support
       negative values of n.

           jq ´[first(range(.)), last(range(.)), nth(./2; range(.))]´
              10
           => [0,9,5]

   first, last, nth(n)
       The first and last functions extract the first and last values from any array at ..

       The nth(n) function extracts the nth value of any array at ..

           jq ´[range(.)]|[first, last, nth(5)]´
              10
           => [0,9,5]

   foreach
       The foreach syntax is similar to reduce, but intended to allow the construction  of  limit
       and reducers that produce intermediate results (see example).

       The  form  is  foreach EXP as $var (INIT; UPDATE; EXTRACT). Like reduce, INIT is evaluated
       once to produce a state value, then each output  of  EXP  is  bound  to  $var,  UPDATE  is
       evaluated  for each output of EXP with the current state and with $var visible. Each value
       output by UPDATE replaces the previous state. Finally, EXTRACT is evaluated for  each  new
       state to extract an output of foreach.

       This  is  mostly  useful only for constructing reduce- and limit-like functions. But it is
       much more general, as it allows for partial reductions (see the example below).

           jq ´[foreach .[] as $item ([[],[]]; if $item == null then [[],.[0]] else [(.[0] + [$item]),[]] end; if $item == null then .[1] else empty end)]´
              [1,2,3,4,null,"a","b",null]
           => [[1,2,3,4],["a","b"]]

   Recursion
       As described above, recurse uses recursion, and any jq  function  can  be  recursive.  The
       while builtin is also implemented in terms of recursion.

       Tail calls are optimized whenever the expression to the left of the recursive call outputs
       its last value. In practice this means that the expression to the left  of  the  recursive
       call should not produce more than one output for each input.

       For example:

           def recurse(f): def r: ., (f | select(. != null) | r); r;

           def while(cond; update):
             def _while:
               if cond then ., (update | _while) else empty end;
             _while;

           def repeat(exp):
             def _repeat:
               exp, _repeat;
             _repeat;

   Generators and iterators
       Some  jq  operators  and  functions are actually generators in that they can produce zero,
       one, or more values for each  input,  just  as  one  might  expect  in  other  programming
       languages  that  have  generators.  For example, .[] generates all the values in its input
       (which must be an array or an object), range(0; 10) generates the integers between  0  and
       10, and so on.

       Even  the  comma  operator  is  a  generator, generating first the values generated by the
       expression to the left of the comma, then for each of those, the values  generate  by  the
       expression on the right of the comma.

       The  empty  builtin  is  the  generator  that  produces  zero  outputs.  The empty builtin
       backtracks to the preceding generator expression.

       All jq functions can be generators just by using builtin generators. It is  also  possible
       to  define  new  generators  using only recursion and the comma operator. If the recursive
       call(s) is(are) "in tail position" then the generator will be efficient.  In  the  example
       below  the  recursive  call by _range to itself is in tail position. The example shows off
       three advanced topics: tail recursion, generator construction, and sub-functions.

           jq ´def range(init; upto; by): def _range: if (by > 0 and . < upto) or (by < 0 and . > upto) then ., ((.+by)|_range) else . end; if by == 0 then init else init|_range end | select((by > 0 and . < upto) or (by < 0 and . > upto)); range(0; 10; 3)´
              null
           => 0, 3, 6, 9

           jq ´def while(cond; update): def _while: if cond then ., (update | _while) else empty end; _while; [while(.<100; .*2)]´
              1
           => [1,2,4,8,16,32,64]

MATH

       jq currently only has IEEE754 double-precision (64-bit) floating point number support.

       Besides simple arithmetic operators such as +, jq also has most  standard  math  functions
       from  the C math library. C math functions that take a single input argument (e.g., sin())
       are available as zero-argument  jq  functions.  C  math  functions  that  take  two  input
       arguments  (e.g.,  pow()) are available as two-argument jq functions that ignore .. C math
       functions that take three input arguments are available  as  three-argument  jq  functions
       that ignore ..

       Availability  of  standard math functions depends on the availability of the corresponding
       math functions in your operating system and C math  library.  Unavailable  math  functions
       will be defined but will raise an error.

       One-input  C  math functions: acos acosh asin asinh atan atanh cbrt ceil cos cosh erf erfc
       exp exp10 exp2 expm1 fabs floor gamma j0 j1 lgamma log log10  log1p  log2  logb  nearbyint
       pow10 rint round significand sin sinh sqrt tan tanh tgamma trunc y0 y1.

       Two-input  C  math functions: atan2 copysign drem fdim fmax fmin fmod frexp hypot jn ldexp
       modf nextafter nexttoward pow remainder scalb scalbln yn.

       Three-input C math functions: fma.

       See your system´s manual for more information on each of these.

I/O

       At this time jq has minimal support for I/O, mostly in  the  form  of  control  over  when
       inputs are read. Two builtins functions are provided for this, input and inputs, that read
       from the same sources (e.g., stdin, files named on the command-line) as jq  itself.  These
       two builtins, and jq´s own reading actions, can be interleaved with each other.

       Two  builtins  provide  minimal  output capabilities, debug, and stderr. (Recall that a jq
       program´s output values are always output as JSON texts on stdout.) The debug builtin  can
       have  application-specific  behavior, such as for executables that use the libjq C API but
       aren´t the jq executable itself. The stderr builtin outputs its input in raw mode to stder
       with no additional decoration, not even a newline.

       Most  jq  builtins  are referentially transparent, and yield constant and repeatable value
       streams when applied to constant inputs. This is not true of I/O builtins.

   input
       Outputs one new input.

   inputs
       Outputs all remaining inputs, one by one.

       This is primarily useful for reductions over a program´s inputs.

   debug
       Causes a debug message based on the input value to be produced. The  jq  executable  wraps
       the  input  value  with ["DEBUG:", <input-value>] and prints that and a newline on stderr,
       compactly. This may change in the future.

   stderr
       Prints its input in raw and compact mode to stderr with no additional decoration, not even
       a newline.

   input_filename
       Returns  the name of the file whose input is currently being filtered. Note that this will
       not work well unless jq is running in a UTF-8 locale.

   input_line_number
       Returns the line number of the input currently being filtered.

STREAMING

       With the --stream option jq can parse input texts in  a  streaming  fashion,  allowing  jq
       programs  to  start  processing  large  JSON texts immediately rather than after the parse
       completes. If you have a single JSON text that is 1GB in size, streaming it will allow you
       to process it much more quickly.

       However,  streaming  isn´t  easy  to  deal  with  as  the  jq  program  will have [<path>,
       <leaf-value>] (and a few other forms) as inputs.

       Several builtins are provided to make handling streams easier.

       The   examples    below    use    the    streamed    form    of    [0,[1]],    which    is
       [[0],0],[[1,0],1],[[1,0]],[[1]].

       Streaming forms include [<path>, <leaf-value>] (to indicate any scalar value, empty array,
       or empty object), and [<path>] (to indicate  the  end  of  an  array  or  object).  Future
       versions  of  jq  run  with  --stream and -seq may output additional forms such as ["error
       message"] when an input text fails to parse.

   truncate_stream(stream_expression)
       Consumes a number as input and truncates the corresponding number of  path  elements  from
       the left of the outputs of the given streaming expression.

           jq ´[1|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]])]´
              1
           => [[[0],2],[[0]]]

   fromstream(stream_expression)
       Outputs values corresponding to the stream expression´s outputs.

           jq ´fromstream(1|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]]))´
              null
           => [2]

   tostream
       The tostream builtin outputs the streamed form of its input.

           jq ´. as $dot|fromstream($dot|tostream)|.==$dot´
              [0,[1,{"a":1},{"b":2}]]
           => true

ASSIGNMENT

       Assignment works a little differently in jq than in most programming languages. jq doesn´t
       distinguish between references to and copies of something -  two  objects  or  arrays  are
       either  equal  or not equal, without any further notion of being "the same object" or "not
       the same object".

       If an object has two fields which are arrays, .foo and .bar, and you append  something  to
       .foo,  then .bar will not get bigger, even if you´ve previously set .bar = .foo. If you´re
       used to programming in languages like Python, Java, Ruby, Javascript, etc.  then  you  can
       think  of  it  as  though  jq  does  a  full  deep copy of every object before it does the
       assignment (for performance it doesn´t actually do that, but that´s the general idea).

       This means that it´s impossible to build circular values in jq (such  as  an  array  whose
       first  element  is  itself).  This  is  quite  intentional, and ensures that anything a jq
       program can produce can be represented in JSON.

       All the assignment operators in jq have path expressions on the left-hand side (LHS).  The
       right-hand  side  (RHS)  provides  values  to  set  to  the  paths  named  by the LHS path
       expressions.

       Values in jq are always immutable. Internally, assignment works by using  a  reduction  to
       compute new, replacement values for . that have had all the desired assignments applied to
       ., then outputting the  modified  value.  This  might  be  made  clear  by  this  example:
       {a:{b:{c:1}}}  |  (.a.b|=3),  ..  This  will  output {"a":{"b":3}} and {"a":{"b":{"c":1}}}
       because the last sub-expression, ., sees the original value, not the modified value.

       Most users will want to use modification assignment operators, such as |=  or  +=,  rather
       than =.

       Note  that the LHS of assignment operators refers to a value in .. Thus $var.foo = 1 won´t
       work as expected ($var.foo is not a valid or useful path expression in .); use $var | .foo
       = 1 instead.

       Note too that .a,.b=0 does not set .a and .b, but (.a,.b)=0 sets both.

   Update-assignment: |=
       This is the "update" operator ´|=´. It takes a filter on the right-hand side and works out
       the new value for the property of . being assigned to by running  the  old  value  through
       this  expression.  For  instance,  (.foo, .bar) |= .+1 will build an object with the "foo"
       field set to the input´s "foo" plus 1, and the "bar" field set to the input´s  "bar"  plus
       1.

       The left-hand side can be any general path expression; see path().

       Note  that the left-hand side of ´|=´ refers to a value in .. Thus $var.foo |= . + 1 won´t
       work as expected ($var.foo is not a valid or useful path expression in .); use $var | .foo
       |= . + 1 instead.

       If  the right-hand side outputs no values (i.e., empty), then the left-hand side path will
       be deleted, as with del(path).

       If the right-hand  side  outputs  multiple  values,  only  the  first  one  will  be  used
       (COMPATIBILITY  NOTE: in jq 1.5 and earlier releases, it used to be that only the last one
       was used).

           jq ´(..|select(type=="boolean")) |= if . then 1 else 0 end´
              [true,false,[5,true,[true,[false]],false]]
           => [1,0,[5,1,[1,[0]],0]]

   Arithmetic update-assignment: +=, -=, *=, /=, %=, //=
       jq has a few operators of the form a op= b, which are all equivalent to a |= . op  b.  So,
       += 1 can be used to increment values, being the same as |= . + 1.

           jq ´.foo += 1´
              {"foo": 42}
           => {"foo": 43}

   Plain assignment: =
       This is the plain assignment operator. Unlike the others, the input to the right-hand-side
       (RHS) is the same as the input to the left-hand-side (LHS) rather than the  value  at  the
       LHS path, and all values output by the RHS will be used (as shown below).

       If the RHS of ´=´ produces multiple values, then for each such value jq will set the paths
       on the left-hand side to the value and then it will output the modified  ..  For  example,
       (.a,.b)=range(2)  outputs {"a":0,"b":0}, then {"a":1,"b":1}. The "update" assignment forms
       (see above) do not do this.

       This example should show the difference between ´=´ and ´|=´:

       Provide input ´{"a": {"b": 10}, "b": 20}´ to the programs:

       .a = .b

       .a |= .b

       The former will set the "a" field of the input to the "b" field of the input, and  produce
       the  output  {"a": 20, "b": 20}. The latter will set the "a" field of the input to the "a"
       field´s "b" field, producing {"a": 10, "b": 20}.

       Another example of the difference between ´=´ and ´|=´:

       null|(.a,.b)=range(3)

       outputs ´{"a":0,"b":0}´, ´{"a":1,"b":1}´, and ´{"a":2,"b":2}´, while

       null|(.a,.b)|=range(3)

       outputs just ´{"a":0,"b":0}´.

   Complex assignments
       Lots more things are allowed on the left-hand  side  of  a  jq  assignment  than  in  most
       languages.  We´ve  already  seen  simple field accesses on the left hand side, and it´s no
       surprise that array accesses work just as well:

           .posts[0].title = "JQ Manual"

       What may come as a surprise is that the  expression  on  the  left  may  produce  multiple
       results, referring to different points in the input document:

           .posts[].comments |= . + ["this is great"]

       That  example  appends  the string "this is great" to the "comments" array of each post in
       the input (where the input is an object with a field "posts" which is an array of posts).

       When jq encounters an assignment like ´a = b´, it records the "path"  taken  to  select  a
       part of the input document while executing a. This path is then used to find which part of
       the input to change while executing  the  assignment.  Any  filter  may  be  used  on  the
       left-hand  side of an equals - whichever paths it selects from the input will be where the
       assignment is performed.

       This is a very powerful operation. Suppose we wanted to add a comment to blog posts, using
       the  same  "blog"  input above. This time, we only want to comment on the posts written by
       "stedolan". We can find those posts using the "select" function described earlier:

           .posts[] | select(.author == "stedolan")

       The paths provided by this operation point to each of the posts that "stedolan" wrote, and
       we can comment on each of them in the same way that we did before:

           (.posts[] | select(.author == "stedolan") | .comments) |=
               . + ["terrible."]

MODULES

       jq has a library/module system. Modules are files whose names end in .jq.

       Modules  imported  by a program are searched for in a default search path (see below). The
       import and include directives allow the importer to alter this path.

       Paths in the a search path are subject to various substitutions.

       For paths starting with "~/", the user´s home directory is substituted for "~".

       For paths starting with "$ORIGIN/", the path of  the  jq  executable  is  substituted  for
       "$ORIGIN".

       For  paths  starting  with  "./"  or paths that are ".", the path of the including file is
       substituted for ".". For  top-level  programs  given  on  the  command-line,  the  current
       directory is used.

       Import directives can optionally specify a search path to which the default is appended.

       The  default  search  path  is  the  search path given to the -L command-line option, else
       ["~/.jq", "$ORIGIN/../lib/jq", "$ORIGIN/../lib"].

       Null and empty string path elements terminate search path processing.

       A dependency with relative path "foo/bar"  would  be  searched  for  in  "foo/bar.jq"  and
       "foo/bar/bar.jq"  in the given search path. This is intended to allow modules to be placed
       in a directory along with, for example, version control files, README files,  and  so  on,
       but also to allow for single-file modules.

       Consecutive  components  with  the  same  name are not allowed to avoid ambiguities (e.g.,
       "foo/foo").

       For example,  with  -L$HOME/.jq  a  module  foo  can  be  found  in  $HOME/.jq/foo.jq  and
       $HOME/.jq/foo/foo.jq.

       If "$HOME/.jq" is a file, it is sourced into the main program.

   import RelativePathString as NAME [<metadata>];
       Imports a module found at the given path relative to a directory in a search path. A ".jq"
       suffix will be added to the relative path string. The module´s symbols are  prefixed  with
       "NAME::".

       The  optional  metadata must be a constant jq expression. It should be an object with keys
       like "homepage" and so on. At this time  jq  only  uses  the  "search"  key/value  of  the
       metadata. The metadata is also made available to users via the modulemeta builtin.

       The  "search"  key in the metadata, if present, should have a string or array value (array
       of strings); this is the search path to be prefixed to the top-level search path.

   include RelativePathString [<metadata>];
       Imports a module found at the given path relative to a directory in a search path as if it
       were  included  in  place.  A  ".jq" suffix will be added to the relative path string. The
       module´s symbols are imported into the caller´s namespace as if the module´s  content  had
       been included directly.

       The  optional  metadata must be a constant jq expression. It should be an object with keys
       like "homepage" and so on. At this time  jq  only  uses  the  "search"  key/value  of  the
       metadata. The metadata is also made available to users via the modulemeta builtin.

   import RelativePathString as $NAME [<metadata>];
       Imports  a  JSON  file found at the given path relative to a directory in a search path. A
       ".json" suffix will be added to  the  relative  path  string.  The  file´s  data  will  be
       available as $NAME::NAME.

       The  optional  metadata must be a constant jq expression. It should be an object with keys
       like "homepage" and so on. At this time  jq  only  uses  the  "search"  key/value  of  the
       metadata. The metadata is also made available to users via the modulemeta builtin.

       The  "search"  key in the metadata, if present, should have a string or array value (array
       of strings); this is the search path to be prefixed to the top-level search path.

   module <metadata>;
       This directive is entirely optional. It´s not required for  proper  operation.  It  serves
       only the purpose of providing metadata that can be read with the modulemeta builtin.

       The  metadata  must  be  a  constant  jq expression. It should be an object with keys like
       "homepage". At this time jq doesn´t use this metadata, but it is made available  to  users
       via the modulemeta builtin.

   modulemeta
       Takes  a  module  name  as  input and outputs the module´s metadata as an object, with the
       module´s imports (including metadata) as an array value for the "deps" key.

       Programs can use this to query a module´s metadata, which they  could  then  use  to,  for
       example, search for, download, and install missing dependencies.

COLORS

       To   configure   alternative  colors  just  set  the  JQ_COLORS  environment  variable  to
       colon-delimited list of partial terminal escape sequences like "1;31", in this order:

       ○   color for null

       ○   color for false

       ○   color for true

       ○   color for numbers

       ○   color for strings

       ○   color for arrays

       ○   color for objects

       The      default      color      scheme      is      the       same       as       setting
       "JQ_COLORS=1;30:0;39:0;39:0;39:0;32:1;39:1;39".

       This  is  not a manual for VT100/ANSI escapes. However, each of these color specifications
       should consist of two numbers separated by a semi-colon, where the first number is one  of
       these:

       ○   1 (bright)

       ○   2 (dim)

       ○   4 (underscore)

       ○   5 (blink)

       ○   7 (reverse)

       ○   8 (hidden)

       and the second is one of these:

       ○   30 (black)

       ○   31 (red)

       ○   32 (green)

       ○   33 (yellow)

       ○   34 (blue)

       ○   35 (magenta)

       ○   36 (cyan)

       ○   37 (white)

BUGS

       Presumably. Report them or discuss them at:

           https://github.com/stedolan/jq/issues

AUTHOR

       Stephen Dolan <mu@netsoc.tcd.ie>

                                           October 2019                                     JQ(1)