diff --git a/NEWS b/NEWS index a4b807e9..32548d33 100644 --- a/NEWS +++ b/NEWS @@ -1,11 +1,12 @@ Release history - * jq version 1.0 was released on Sun Oct 21 2012 - * jq version 1.1 was released on Sun Oct 21 2012 - * jq version 1.2 was released on Thu Dec 20 2012 - * jq version 1.3 was released on Sun May 19 2013 + * jq version 1.5 was released on Sat Aug 15 2015 * jq version 1.4 was released on Mon Jun 9 2014 + * jq version 1.3 was released on Sun May 19 2013 + * jq version 1.2 was released on Thu Dec 20 2012 + * jq version 1.1 was released on Sun Oct 21 2012 + * jq version 1.0 was released on Sun Oct 21 2012 New features in 1.5 since 1.4: diff --git a/docs/content/2.download/default.yml b/docs/content/2.download/default.yml index 67abe245..c857ea1b 100644 --- a/docs/content/2.download/default.yml +++ b/docs/content/2.download/default.yml @@ -30,6 +30,11 @@ body: [ArchWiki](https://wiki.archlinux.org/index.php/Arch_User_Repository) for how to install from AUR. + * jq 1.5 binaries for + [64-bit](https://github.com/stedolan/jq/releases/download/jq-1.5/jq-linux64) + or + [32-bit](https://github.com/stedolan/jq/releases/download/jq-1.5/jq-linux32). + * jq 1.4 binaries for [64-bit](https://github.com/stedolan/jq/releases/download/jq-1.4/jq-linux-x86_64) or @@ -42,9 +47,8 @@ body: ### OS X - * Use [Homebrew](http://brew.sh/) to install jq 1.4 with - `brew install jq`. You can also install 1.5rc2 with - `brew install --devel jq`. + * Use [Homebrew](http://brew.sh/) to install jq 1.5 with + `brew install jq`. * jq 1.4 binaries for [64-bit](https://github.com/stedolan/jq/releases/download/jq-1.4/jq-osx-x86_64) @@ -71,6 +75,11 @@ body: * Use [Chocolatey NuGet](https://chocolatey.org/) to install jq 1.4 with `chocolatey install jq`. + * jq 1.5 executables for + [64-bit](https://github.com/stedolan/jq/releases/download/jq-1.5/jq-win64.exe) + or + [32-bit](https://github.com/stedolan/jq/releases/download/jq-1.5/jq-win32.exe). + * jq 1.4 executables for [64-bit](https://github.com/stedolan/jq/releases/download/jq-1.4/jq-win64.exe) or @@ -89,7 +98,7 @@ body: ### From source on Linux, OS X, Cygwin, and other POSIX-like operating systems - * [Source tarball for jq 1.4](https://github.com/stedolan/jq/archive/jq-1.4.tar.gz) + * [Source tarball for jq 1.5](https://github.com/stedolan/jq/archive/jq-1.5.tar.gz) You can build it using the usual `./configure && make && sudo make install` rigmarole. @@ -99,15 +108,13 @@ body: git clone https://github.com/stedolan/jq.git cd jq autoreconf -i - ./configure + ./configure --disable-maintainer-mode make sudo make install To build it from a git clone, you'll need to install a few packages first: - * [Flex](http://flex.sourceforge.net/) - * [Bison](https://www.gnu.org/software/bison/) * [GCC](https://gcc.gnu.org) * [Make](https://www.gnu.org/software/make/) * [Autotools](https://www.gnu.org/software/automake/) @@ -122,10 +129,11 @@ body: by Apple. This can be found in [Homebrew](http://brew.sh) or [MacPorts](https://macports.org/). - Flex and Bison are used to generate the lexer and parser for jq. For jq - 1.5, neither is required if you use `./configure - --disable-maintainer-mode` instead of `./configure`. This flag says to use - the pre-generated lexer and parser that come with the code. + The `--disable-maintainer-mode` flag says to use the pre-generated lexer + and parser that come with the code. To compile the lexer and parser also + from source, leave out this flag. You will need to install + [Flex](http://flex.sourceforge.net/) and + [Bison](https://www.gnu.org/software/bison/). #### Building the documentation diff --git a/docs/content/3.manual/manual.yml b/docs/content/3.manual/manual.yml index 13d96766..6c6d7554 100644 --- a/docs/content/3.manual/manual.yml +++ b/docs/content/3.manual/manual.yml @@ -3,8 +3,8 @@ headline: jq Manual (development version) history: | - *For released versions, see [jq 1.4](/jq/manual/v1.4) or - [jq 1.3](/jq/manual/v1.3).* + *For released versions, see [jq 1.5](/jq/manual/v1.5), + [jq 1.4](/jq/manual/v1.4) or [jq 1.3](/jq/manual/v1.3).* body: | diff --git a/docs/content/3.manual/v1.5/manual.yml b/docs/content/3.manual/v1.5/manual.yml new file mode 100644 index 00000000..1e42eac8 --- /dev/null +++ b/docs/content/3.manual/v1.5/manual.yml @@ -0,0 +1,2878 @@ +--- +headline: jq Manual (development version) + +history: | + + *The manual for the development version of jq can be found + [here](/jq/manual).* + +body: | + + 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: + +manpage_intro: | + jq(1) -- Command-line JSON processor + ==================================== + + ## SYNOPSIS + + `jq` [...] [...] + + `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 may be specified, in + which case `jq` will read input from those instead. + + The are described in the [INVOKING JQ] section; they + mostly concern input and output formatting. The is written + in the jq language and specifies how to transform the input + file or document. + + ## FILTERS + +manpage_epilogue: | + ## BUGS + + Presumably. Report them or discuss them at: + + https://github.com/stedolan/jq/issues + + ## AUTHOR + + Stephen Dolan `` + +sections: + - title: Invoking jq + body: | + + 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 more 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`. + + * `--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. + + * `--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"`. + + * `--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 + `$foo` is available in the program and has the value `123`. + + * `--slurpfile variable-name filename`: + + This option reads all the JSON texts in the named file and binds + an array of the parsed JSON values to the given global variable. + If you run jq with `--argfile foo bar`, then `$foo` is available + in the program and has an array whose elements correspond to the + texts 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`.) + + * `--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. + + - title: Basic filters + entries: + - title: "`.`" + body: | + + The absolute simplest (and least interesting) filter + is `.`. This is a filter that takes its input and + produces it unchanged as output. + + Since jq by default pretty-prints all output, this trivial + program can be a useful way of formatting JSON output from, + say, `curl`. + + examples: + - program: '.' + input: '"Hello, world!"' + output: ['"Hello, world!"'] + + - title: "`.foo`, `.foo.bar`" + body: | + + 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. + + If the key contains special characters, you need to surround + it with double quotes like this: `."foo$"`. + + A filter of the form `.foo.bar` is equivalent to `.foo|.bar`. + + examples: + - program: '.foo' + input: '{"foo": 42, "bar": "less interesting data"}' + output: [42] + - program: '.foo' + input: '{"notfoo": true, "alsonotfoo": false}' + output: ['null'] + - program: '.["foo"]' + input: '{"foo": 42}' + output: [42] + + - title: "`.foo?`" + body: | + + Just like `.foo`, but does not output even an error when `.` + is not an array or an object. + + examples: + - program: '.foo?' + input: '{"foo": 42, "bar": "less interesting data"}' + output: [42] + - program: '.foo?' + input: '{"notfoo": true, "alsonotfoo": false}' + output: ['null'] + - program: '.["foo"]?' + input: '{"foo": 42}' + output: [42] + - program: '[.foo?]' + input: '[1,2]' + output: ['[]'] + + - title: "`.[]`, `.[2]`, `.[10:15]`" + body: | + + You can also look up fields of an object using syntax like + `.["foo"]` (.foo above is a shorthand version of this). This + one works for arrays as well, if the key is an + integer. Arrays are zero-based (like javascript), so `.[2]` + returns the third element of the array. + + 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). + + The `.[2]` syntax can be used to return the element at the + given index. Negative indices are allowed, with -1 referring + to the last element, -2 referring to the next to last element, + and so on. + + The `.foo` syntax only works for simply keys i.e. keys that + are all alphanumeric characters. `.[]` works with + keys that contain special characters such as colons and dots. + For example `.["foo::bar"]` and `.["foo.bar"]` work while + `.foo::bar` and `.foo.bar` would not. + + The `?` "operator" can also be used with the slice operator, + as in `.[10:15]?`, which outputs values where the inputs are + slice-able. + + examples: + - program: '.[0]' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: ['{"name":"JSON", "good":true}'] + + - program: '.[2]' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: ['null'] + + - program: '.[2:4]' + input: '["a","b","c","d","e"]' + output: ['["c", "d"]'] + + - program: '.[2:4]' + input: '"abcdefghi"' + output: ['"cd"'] + + - program: '.[:3]' + input: '["a","b","c","d","e"]' + output: ['["a", "b", "c"]'] + + - program: '.[-2:]' + input: '["a","b","c","d","e"]' + output: ['["d", "e"]'] + + - program: '.[-2]' + input: '[1,2,3]' + output: ['2'] + + - title: "`.[]`" + body: | + + 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. + + examples: + - program: '.[]' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: + - '{"name":"JSON", "good":true}' + - '{"name":"XML", "good":false}' + + - program: '.[]' + input: '[]' + output: [] + + - program: '.[]' + input: '{"a": 1, "b": 1}' + output: ['1', '1'] + + - title: "`.[]?`" + body: | + + Like `.[]`, but no errors will be output if . is not an array + or object. + + - title: "`,`" + body: | + + If two filters are separated by a comma, then the + input will be fed into both and there will be multiple + outputs: 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. + + examples: + - program: '.foo, .bar' + input: '{"foo": 42, "bar": "something else", "baz": true}' + output: ['42', '"something else"'] + + - program: ".user, .projects[]" + input: '{"user":"stedolan", "projects": ["jq", "wikiflow"]}' + output: ['"stedolan"', '"jq"', '"wikiflow"'] + + - program: '.[4,2]' + input: '["a","b","c","d","e"]' + output: ['"e"', '"c"'] + + - title: "`|`" + body: | + 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. + + examples: + - program: '.[] | .name' + input: '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' + output: ['"JSON"', '"XML"'] + + - title: Types and Values + body: | + + 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. + + entries: + - title: Array construction - `[]` + body: | + + As in JSON, `[]` is used to construct arrays, as in + `[1,2,3]`. The elements of the arrays can be any jq + expression. 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. + + examples: + - program: "[.user, .projects[]]" + input: '{"user":"stedolan", "projects": ["jq", "wikiflow"]}' + output: ['["stedolan", "jq", "wikiflow"]'] + - title: Objects - `{}` + body: | + + Like JSON, `{}` is for constructing objects (aka + dictionaries or hashes), as in: `{"a": 42, "b": 17}`. + + If the keys are "sensible" (all alphabetic characters), then + the quotes can be left off. 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}`. 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's so common, there's a shortcut syntax: `{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"]} + + examples: + - program: '{user, title: .titles[]}' + input: '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' + output: + - '{"user":"stedolan", "title": "JQ Primer"}' + - '{"user":"stedolan", "title": "More JQ"}' + - program: '{(.user): .titles}' + input: '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' + output: ['{"stedolan": ["JQ Primer", "More JQ"]}'] + + - title: Builtin operators and functions + body: | + + 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. + + entries: + - title: Addition - `+` + body: | + + 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. + + examples: + - program: '.a + 1' + input: '{"a": 7}' + output: ['8'] + - program: '.a + .b' + input: '{"a": [1,2], "b": [3,4]}' + output: ['[1,2,3,4]'] + - program: '.a + null' + input: '{"a": 1}' + output: ['1'] + - program: '.a + 1' + input: '{}' + output: ['1'] + - program: '{a: 1} + {b: 2} + {c: 3} + {a: 42}' + input: 'null' + output: ['{"a": 42, "b": 2, "c": 3}'] + + - title: Subtraction - `-` + body: | + + 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. + + examples: + - program: '4 - .a' + input: '{"a":3}' + output: ['1'] + - program: . - ["xml", "yaml"] + input: '["xml", "yaml", "json"]' + output: ['["json"]'] + + - title: Multiplication, division, modulo - `*`, `/`, and `%` + body: | + + 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. + + examples: + - program: '10 / . * 3' + input: 5 + output: [6] + - program: '. / ", "' + input: '"a, b,c,d, e"' + output: ['["a","b,c,d","e"]'] + - program: '{"k": {"a": 1, "b": 2}} * {"k": {"a": 0,"c": 3}}' + input: 'null' + output: ['{"k": {"a": 0, "b": 2, "c": 3}}'] + - program: '.[] | (1 / .)?' + input: '[1,0,-1]' + output: ['1', '-1'] + + + - title: "`length`" + body: | + + 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. + + examples: + - program: '.[] | length' + input: '[[1,2], "string", {"a":2}, null]' + output: [2, 6, 1, 0] + + - title: "`keys`, `keys_unsorted`" + body: | + + 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. + + examples: + - program: 'keys' + input: '{"abc": 1, "abcd": 2, "Foo": 3}' + output: ['["Foo", "abc", "abcd"]'] + - program: 'keys' + input: '[42,3,35]' + output: ['[0,1,2]'] + + - title: "`has(key)`" + body: | + + 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. + + examples: + - program: 'map(has("foo"))' + input: '[{"foo": 42}, {}]' + output: ['[true, false]'] + - program: 'map(has(2))' + input: '[[0,1], ["a","b","c"]]' + output: ['[false, true]'] + + - title: "`in`" + body: | + + The builtin function `in` returns 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`. + + examples: + - program: '.[] | in({"foo": 42})' + input: '["foo", "bar"]' + output: ['true', 'false'] + - program: 'map(in([0,1]))' + input: '[2, 0]' + output: ['[false, true]'] + + - title: "`path(path_expression)`" + body: | + + Outputs array representations of the given path expression + in `.`. The outputs are arrays of strings (keys in objects0 + 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. + + examples: + - program: 'path(.a[0].b)' + input: 'null' + output: ['["a",0,"b"]'] + - program: '[path(..)]' + input: '{"a":[{"b":1}]}' + output: ['[[],["a"],["a",0],["a",0,"b"]]'] + + - title: "`del(path_expression)`" + body: | + + The builtin function `del` removes a key and its corresponding + value from an object. + + examples: + - program: 'del(.foo)' + input: '{"foo": 42, "bar": 9001, "baz": 42}' + output: ['{"bar": 9001, "baz": 42}'] + - program: 'del(.[1, 2])' + input: '["foo", "bar", "baz"]' + output: ['["foo"]'] + + - title: "`to_entries`, `from_entries`, `with_entries`" + body: | + + 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, value and Value as keys. + + examples: + - program: 'to_entries' + input: '{"a": 1, "b": 2}' + output: ['[{"key":"a", "value":1}, {"key":"b", "value":2}]'] + - program: 'from_entries' + input: '[{"key":"a", "value":1}, {"key":"b", "value":2}]' + output: ['{"a": 1, "b": 2}'] + - program: 'with_entries(.key |= "KEY_" + .)' + input: '{"a": 1, "b": 2}' + output: ['{"KEY_a": 1, "KEY_b": 2}'] + + + - title: "`select(boolean_expression)`" + body: | + + 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]`. + + examples: + - program: 'map(select(. >= 2))' + input: '[1,5,3,0,7]' + output: ['[5,3,7]'] + - program: '.[] | select(.id == "second")' + input: '[{"id": "first", "val": 1}, {"id": "second", "val": 2}]' + output: ['{"id": "second", "val": 2}'] + + + - title: "`arrays`, `objects`, `iterables`, `booleans`, `numbers`, `normals`, `finites`, `strings`, `nulls`, `values`, `scalars`" + body: | + + 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. + + examples: + - program: '.[]|numbers' + input: '[[],{},1,"foo",null,true,false]' + output: ['1'] + + - title: "`empty`" + body: | + + `empty` returns no results. None at all. Not even `null`. + + It's useful on occasion. You'll know if you need it :) + + examples: + - program: '1, empty, 2' + input: 'null' + output: [1, 2] + - program: '[1,2,empty,3]' + input: 'null' + output: ['[1,2,3]'] + + - title: "`error(message)`" + body: | + + 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. + + - title: "`$__loc__`" + body: | + + Produces an object with a "file" key and a "line" key, with + the filename and line number where `$__loc__` occurs, as + values. + + examples: + - program: 'try error("\($__loc__)") catch .' + input: 'null' + output: ['"{\"file\":\"\",\"line\":1}"'] + + - title: "`map(x)`, `map_values(x)`" + body: | + + For any filter `x`, `map(x)` will run that filter for each + element of the input array, and produce the outputs 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`. + + examples: + - program: 'map(.+1)' + input: '[1,2,3]' + output: ['[2,3,4]'] + + - program: 'map_values(.+1)' + input: '{"a": 1, "b": 2, "c": 3}' + output: ['{"a": 2, "b": 3, "c": 4}'] + + - title: "`paths`, `paths(node_filter)`, `leaf_paths`" + body: | + + `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. + + examples: + - program: '[paths]' + input: '[1,[[],{"a":2}]]' + output: ['[[0],[1],[1,0],[1,1],[1,1,"a"]]'] + - program: '[paths(scalars)]' + input: '[1,[[],{"a":2}]]' + output: ['[[0],[1,1,"a"]]'] + + - title: "`add`" + body: | + + 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`. + + examples: + - program: add + input: '["a","b","c"]' + output: ['"abc"'] + - program: add + input: '[1, 2, 3]' + output: [6] + - program: add + input: '[]' + output: ["null"] + + - title: "`any`, `any(condition)`, `any(generator; condition)`" + body: | + + The filter `any` takes as input an array of boolean values, + and produces `true` as output if any of the the elements of + the array is `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. + + examples: + - program: any + input: '[true, false]' + output: ["true"] + - program: any + input: '[false, false]' + output: ["false"] + - program: any + input: '[]' + output: ["false"] + + - title: "`all`, `all(condition)`, `all(generator; condition)`" + body: | + + The filter `all` takes as input an array of boolean values, + and produces `true` as output if all of the 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`. + + examples: + - program: all + input: '[true, false]' + output: ["false"] + - program: all + input: '[true, true]' + output: ["true"] + - program: all + input: '[]' + output: ["true"] + + - title: "\\[Requires 1.5\\] `flatten`, `flatten(depth)`" + body: | + + 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. + + examples: + - program: flatten + input: '[1, [2], [[3]]]' + output: ["[1, 2, 3]"] + - program: flatten(1) + input: '[1, [2], [[3]]]' + output: ["[1, 2, [3]]"] + - program: flatten + input: '[[]]' + output: ["[]"] + - program: flatten + input: '[{"foo": "bar"}, [{"foo": "baz"}]]' + output: ['[{"foo": "bar"}, {"foo": "baz"}]'] + + - title: "`range(upto)`, `range(from;upto)` `range(from;upto;by)`" + body: | + + 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`. + + examples: + - program: 'range(2;4)' + input: 'null' + output: ['2', '3'] + - program: '[range(2;4)]' + input: 'null' + output: ['[2,3]'] + - program: '[range(4)]' + input: 'null' + output: ['[0,1,2,3]'] + - program: '[range(0;10;3)]' + input: 'null' + output: ['[0,3,6,9]'] + - program: '[range(0;10;-1)]' + input: 'null' + output: ['[]'] + - program: '[range(0;-5;-1)]' + input: 'null' + output: ['[0,-1,-2,-3,-4]'] + + - title: "`floor`" + body: | + + The `floor` function returns the floor of its numeric input. + + examples: + - program: 'floor' + input: '3.14159' + output: ['3'] + + - title: "`sqrt`" + body: | + + The `sqrt` function returns the square root of its numeric input. + + examples: + - program: 'sqrt' + input: '9' + output: ['3'] + + - title: "`tonumber`" + body: | + + 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. + + examples: + - program: '.[] | tonumber' + input: '[1, "1"]' + output: [1, 1] + + - title: "`tostring`" + body: | + + The `tostring` function prints its input as a + string. Strings are left unchanged, and all other values are + JSON-encoded. + + examples: + - program: '.[] | tostring' + input: '[1, "1", [1]]' + output: ['"1"', '"1"', '"[1]"'] + + - title: "`type`" + body: | + + The `type` function returns the type of its argument as a + string, which is one of null, boolean, number, string, array + or object. + + examples: + - program: 'map(type)' + input: '[0, false, [], {}, null, "hello"]' + output: ['["number", "boolean", "array", "object", "null", "string"]'] + + - title: "`infinite`, `nan`, `isinfinite`, `isnan`, `isfinite`, `isnormal`" + body: | + + 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. + + examples: + - program: '.[] | (infinite * .) < 0' + input: '[-1, 1]' + output: ['true', 'false'] + - program: 'infinite, nan | type' + input: 'null' + output: ['"number"', '"number"'] + + - title: "`sort, sort_by(path_expression)`" + body: | + + The `sort` functions sorts its input, which must be an + array. Values are sorted in the following order: + + * `null` + * `false` + * `true` + * 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. + + examples: + - program: 'sort' + input: '[8,3,null,6]' + output: ['[null,3,6,8]'] + - program: 'sort_by(.foo)' + input: '[{"foo":4, "bar":10}, {"foo":3, "bar":100}, {"foo":2, "bar":1}]' + output: ['[{"foo":2, "bar":1}, {"foo":3, "bar":100}, {"foo":4, "bar":10}]'] + + - title: "`group_by(path_expression)`" + body: | + + `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. + + examples: + - program: 'group_by(.foo)' + input: '[{"foo":1, "bar":10}, {"foo":3, "bar":100}, {"foo":1, "bar":1}]' + output: ['[[{"foo":1, "bar":10}, {"foo":1, "bar":1}], [{"foo":3, "bar":100}]]'] + + - title: "`min`, `max`, `min_by(path_exp)`, `max_by(path_exp)`" + body: | + + 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. + + examples: + - program: 'min' + input: '[5,4,2,7]' + output: ['2'] + - program: 'max_by(.foo)' + input: '[{"foo":1, "bar":14}, {"foo":2, "bar":3}]' + output: ['{"foo":2, "bar":3}'] + + - title: "`unique`, `unique_by(path_exp)`" + body: | + + 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`. + + examples: + - program: 'unique' + input: '[1,2,5,3,5,3,1,3]' + output: ['[1,2,3,5]'] + - program: 'unique_by(.foo)' + input: '[{"foo": 1, "bar": 2}, {"foo": 1, "bar": 3}, {"foo": 4, "bar": 5}]' + output: ['[{"foo": 1, "bar": 2}, {"foo": 4, "bar": 5}]'] + - program: 'unique_by(length)' + input: '["chunky", "bacon", "kitten", "cicada", "asparagus"]' + output: ['["bacon", "chunky", "asparagus"]'] + + - title: "`reverse`" + body: | + + This function reverses an array. + + examples: + - program: 'reverse' + input: '[1,2,3,4]' + output: ['[4,3,2,1]'] + + - title: "`contains(element)`" + body: | + + 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. + + examples: + - program: 'contains("bar")' + input: '"foobar"' + output: ['true'] + - program: 'contains(["baz", "bar"])' + input: '["foobar", "foobaz", "blarp"]' + output: ['true'] + - program: 'contains(["bazzzzz", "bar"])' + input: '["foobar", "foobaz", "blarp"]' + output: ['false'] + - program: 'contains({foo: 12, bar: [{barp: 12}]})' + input: '{"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}' + output: ['true'] + - program: 'contains({foo: 12, bar: [{barp: 15}]})' + input: '{"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]}' + output: ['false'] + + - title: "`indices(s)`" + body: | + + 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`. + + examples: + - program: 'indices(", ")' + input: '"a,b, cd, efg, hijk"' + output: ['[3,7,12]'] + - program: 'indices(1)' + input: '[0,1,2,1,3,1,4]' + output: ['[1,3,5]'] + - program: 'indices([1,2])' + input: '[0,1,2,3,1,4,2,5,1,2,6,7]' + output: ['[1,8]'] + + - title: "`index(s)`, `rindex(s)`" + body: | + + Outputs the index of the first (`index`) or last (`rindex`) + occurrence of `s` in the input. + + examples: + - program: 'index(", ")' + input: '"a,b, cd, efg, hijk"' + output: ['3'] + - program: 'rindex(", ")' + input: '"a,b, cd, efg, hijk"' + output: ['12'] + + - title: "`inside`" + body: | + + The filter `inside(b)` will produce true if the input is + completely contained within b. It is, essentially, an + inversed version of `contains`. + + examples: + - program: 'inside("foobar")' + input: '"bar"' + output: ['true'] + - program: 'inside(["foobar", "foobaz", "blarp"])' + input: '["baz", "bar"]' + output: ['true'] + - program: 'inside(["foobar", "foobaz", "blarp"])' + input: '["bazzzzz", "bar"]' + output: ['false'] + - program: 'inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})' + input: '{"foo": 12, "bar": [{"barp": 12}]}' + output: ['true'] + - program: 'inside({"foo": 12, "bar":[1,2,{"barp":12, "blip":13}]})' + input: '{"foo": 12, "bar": [{"barp": 15}]}' + output: ['false'] + + - title: "`startswith(str)`" + body: | + + Outputs `true` if . starts with the given string argument. + + examples: + - program: '[.[]|startswith("foo")]' + input: '["fo", "foo", "barfoo", "foobar", "barfoob"]' + output: ['[false, true, false, true, false]'] + + - title: "`endswith(str)`" + body: | + + Outputs `true` if . ends with the given string argument. + + examples: + - program: '[.[]|endswith("foo")]' + input: '["foobar", "barfoo"]' + output: ['[false, true]'] + + - title: "`combinations`, `combinations(n)`" + body: | + + 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. + + examples: + - program: 'combinations' + input: '[[1,2], [3, 4]]' + output: ['[1, 3]', '[1, 4]', '[2, 3]', '[2, 4]'] + - program: 'combinations(2)' + input: '[0, 1]' + output: ['[0, 0]', '[0, 1]', '[1, 0]', '[1, 1]'] + + - title: "`ltrimstr(str)`" + body: | + + Outputs its input with the given prefix string removed, if it + starts with it. + + examples: + - program: '[.[]|ltrimstr("foo")]' + input: '["fo", "foo", "barfoo", "foobar", "afoo"]' + output: ['["fo","","barfoo","bar","afoo"]'] + + - title: "`rtrimstr(str)`" + body: | + + Outputs its input with the given suffix string removed, if it + ends with it. + + examples: + - program: '[.[]|rtrimstr("foo")]' + input: '["fo", "foo", "barfoo", "foobar", "foob"]' + output: ['["fo","","bar","foobar","foob"]'] + + - title: "`explode`" + body: | + + Converts an input string into an array of the string's + codepoint numbers. + + examples: + - program: 'explode' + input: '"foobar"' + output: ['[102,111,111,98,97,114]'] + + - title: "`implode`" + body: | + + The inverse of explode. + + examples: + - program: 'implode' + input: '[65, 66, 67]' + output: ['"ABC"'] + + - title: "`split`" + body: | + + Splits an input string on the separator argument. + + examples: + - program: 'split(", ")' + input: '"a, b,c,d, e, "' + output: ['["a","b,c,d","e",""]'] + + - title: "`join(str)`" + body: | + + 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. + + examples: + - program: 'join(", ")' + input: '["a","b,c,d","e"]' + output: ['"a, b,c,d, e"'] + + + - title: "`ascii_downcase`, `ascii_upcase`" + body: | + + Emit a copy of the input string with its alphabetic characters (a-z and A-Z) + converted to the specified case. + + example: + - program: 'ascii_upcase' + input: '"useful but not for é"' + output: '"USEFUL BUT NOT FOR é"' + + - title: "`while(cond; update)`" + body: | + + 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. + + examples: + - program: '[while(.<100; .*2)]' + input: '1' + output: ['[1,2,4,8,16,32,64]'] + + - title: "`until(cond; next)`" + body: | + + 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. + + examples: + - program: '[.,1]|until(.[0] < 1; [.[0] - 1, .[1] * .[0]])|.[1]' + input: '4' + output: ['24'] + + + - title: "`recurse(f)`, `recurse`, `recurse(f; condition)`, `recurse_down`" + body: | + + 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. + + examples: + - program: 'recurse(.foo[])' + input: '{"foo":[{"foo": []}, {"foo":[{"foo":[]}]}]}' + output: + - '{"foo":[{"foo":[]},{"foo":[{"foo":[]}]}]}' + - '{"foo":[]}' + - '{"foo":[{"foo":[]}]}' + - '{"foo":[]}' + + - program: 'recurse' + input: '{"a":0,"b":[1]}' + output: + - '{"a":0,"b":[1]}' + - '0' + - '[1]' + - '1' + + - program: 'recurse(. * .; . < 20)' + input: 2 + output: + - 2 + - 4 + - 16 + + - title: "`..`" + body: | + + Short-hand for `recurse` without arguments. 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" `.`. + + examples: + - program: '..|.a?' + input: '[[{"a":1}]]' + output: ['1'] + + - title: "`env`" + body: | + + Outputs an object representing jq's environment. + + examples: + - program: 'env.PAGER' + input: 'null' + output: ['"less"'] + + - title: "`transpose`" + body: | + + Transpose a possibly jagged matrix (an array of arrays). + Rows are padded with nulls so the result is always rectangular. + + examples: + - program: 'transpose' + input: '[[1], [2,3]]' + output: ['[[1,2],[null,3]]'] + + - title: "`bsearch(x)`" + body: | + + 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. + + examples: + - program: 'bsearch(0)' + input: '[0,1]' + output: ['0'] + - program: 'bsearch(0)' + input: '[1,2,3]' + output: ['-1'] + - program: 'bsearch(4) as $ix | if $ix < 0 then .[-(1+$ix)] = 4 else . end' + input: '[1,2,3]' + output: ['[1,2,3,4]'] + + - title: "String interpolation - `\\(foo)`" + body: | + + Inside a string, you can put an expression inside parens + after a backslash. Whatever the expression returns will be + interpolated into the string. + + examples: + - program: '"The input was \(.), which is one less than \(.+1)"' + input: '42' + output: ['"The input was 42, which is one less than 43"'] + + - title: "Convert to/from JSON" + body: | + + 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. + + examples: + - program: '[.[]|tostring]' + input: '[1, "foo", ["foo"]]' + output: ['["1","foo","[\"foo\"]"]'] + - program: '[.[]|tojson]' + input: '[1, "foo", ["foo"]]' + output: ['["1","\"foo\"","[\"foo\"]"]'] + - program: '[.[]|tojson|fromjson]' + input: '[1, "foo", ["foo"]]' + output: ['[1,"foo",["foo"]]'] + + - title: "Format strings and escaping" + body: | + + 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`: + + Calls `tostring`, see that function for details. + + * `@json`: + + Serializes the input as JSON. + + * `@html`: + + Applies HTML/XML escaping, by mapping the characters + `<>&'"` to their entity equivalents `<`, `>`, + `&`, `'`, `"`. + + * `@uri`: + + Applies percent-encoding, by mapping all reserved URI + characters to a `%XX` sequence. + + * `@csv`: + + The input must be an array, and it is rendered as CSV + with double quotes for strings, and quotes escaped by + repetition. + + * `@tsv`: + + The input must be an array, and it is rendered as TSV + (tab-separated values). Each input array will be printed as + a single line. Fields are separated by a single + tab (ascii `0x09`). Input characters line-feed (ascii `0x0a`), + carriage-return (ascii `0x0d`), tab (ascii `0x09`) and + backslash (ascii `0x5c`) will be output as escape sequences + `\n`, `\r`, `\t`, `\\` respectively. + + * `@sh`: + + The input is escaped suitable for use in a command-line + for a POSIX shell. If the input is an array, the output + will be a series of space-separated strings. + + * `@base64`: + + The input is converted to base64 as specified by RFC 4648. + + 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. + + examples: + - program: '@html' + input: '"This works if x < y"' + output: ['"This works if x < y"'] + +# - program: '@html "Anonymous said: \(.)"' +# input: '""' +# output: ["Anonymous said: <script>alert("lol hax");</script>"] + + - program: '@sh "echo \(.)"' + input: "\"O'Hara's Ale\"" + output: ["\"echo 'O'\\\\''Hara'\\\\''s Ale'\""] + + - title: "Dates" + body: | + + 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`, `mktime`, and `gmtime`. + 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 + time as an array of numbers representing (in this order): the + year, the month (zero-based), the day of the month, 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 `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 with the given + format. + + 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. + + examples: + - program: 'fromdate' + input: '"2015-03-05T23:51:47Z"' + output: ['1425599507'] + + - program: 'strptime("%Y-%m-%dT%H:%M:%SZ")' + input: '"2015-03-05T23:51:47Z"' + output: ['[2015,2,5,23,51,47,4,63]'] + + - program: 'strptime("%Y-%m-%dT%H:%M:%SZ")|mktime' + input: '"2015-03-05T23:51:47Z"' + output: ['1425599507'] + + - title: Conditionals and Comparisons + entries: + - title: "`==`, `!=`" + body: | + + 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' + + examples: + - program: '.[] == 1' + input: '[1, 1.0, "1", "banana"]' + output: ['true', 'true', 'false', 'false'] + + - title: if-then-else + body: | + + `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, it is + considered "true" if any of those results is not false or + null. If it produces zero results, it's considered false. + + More cases can be added to an if using `elif A then B` syntax. + + examples: + - program: |- + if . == 0 then + "zero" + elif . == 1 then + "one" + else + "many" + end + input: 2 + output: ['"many"'] + + - title: "`>, >=, <=, <`" + body: | + + 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. + + examples: + - program: '. < 5' + input: 2 + output: ['true'] + + - title: and/or/not + body: | + + 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. + + examples: + - program: '42 and "a string"' + input: 'null' + output: ['true'] + - program: '(true, false) or false' + input: 'null' + output: ['true', 'false'] +# - program: '(true, false) and (true, false)' +# input: 'null' +# output: ['true', 'false', 'false', 'false'] + - program: '(true, true) and (true, false)' + input: 'null' + output: ['true', 'false', 'true', 'false'] + - program: '[true, false | not]' + input: 'null' + output: ['[false, true]'] + + - title: Alternative operator - `//` + body: | + + 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). + + examples: + - program: '.foo // 42' + input: '{"foo": 19}' + output: [19] + - program: '.foo // 42' + input: '{}' + output: [42] + + - title: try-catch + body: | + + 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. + + examples: + - program: 'try .a catch ". is not an object"' + input: 'true' + output: ['". is not an object"'] + - program: '[.[]|try .a]' + input: '[{}, true, {"a":1}]' + output: ['[null, 1]'] + - program: 'try error("some exception") catch .' + input: 'true' + output: ['"some exception"'] + + - title: Breaking out of control structures + body: | + + 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. + + - title: "`?` operator" + body: | + + The `?` operator, used as `EXP?`, is shorthand for `try EXP`. + + examples: + - program: '[.[]|(.a)?]' + input: '[{}, true, {"a":1}]' + output: ['[null, 1]'] + + + - title: Regular expressions (PCRE) + body: | + + 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. + + entries: + - title: "\\[Requires 1.5\\] `test(val)`, `test(regex; flags)`" + body: | + + Like `match`, but does not return match objects, only `true` or `false` + for whether or not the regex matches the input. + + examples: + - program: 'test("foo")' + input: '"foo"' + output: ['true'] + - program: '.[] | test("a b c # spaces are ignored"; "ix")' + input: '["xabcd", "ABC"]' + output: ['true', 'true'] + + - title: "\\[Requires 1.5\\] `match(val)`, `match(regex; flags)`" + body: | + + **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 + + examples: + - program: 'match("(abc)+"; "g")' + input: '"abc abc"' + output: + - '{"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}]}' + - program: 'match("foo")' + input: '"foo bar foo"' + output: ['{"offset": 0, "length": 3, "string": "foo", "captures": []}'] + - program: 'match(["foo", "ig"])' + input: '"foo bar FOO"' + output: + - '{"offset": 0, "length": 3, "string": "foo", "captures": []}' + - '{"offset": 8, "length": 3, "string": "FOO", "captures": []}' + - program: 'match("foo (?bar)? foo"; "ig")' + input: '"foo bar foo foo foo"' + output: + - '{"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"}]}' + + - program: '[ match("."; "g")] | length' + input: '"abc"' + output: [3] + + + - title: "\\[Requires 1.5\\] `capture(val)`, `capture(regex; flags)`" + body: | + + 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. + + examples: + - program: 'capture("(?[a-z]+)-(?[0-9]+)")' + input: '"xyzzy-14"' + output: ['{ "a": "xyzzy", "n": "14" }'] + + - title: "\\[Requires 1.5\\] `scan(regex)`, `scan(regex; flags)`" + body: | + + 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) ]`. + + example: + - program: 'scan("c")' + input: '"abcdefabc"' + output: ['"c"', '"c"'] + + - program: 'scan("b")' + input: ("", "") + output: ['[]', '[]'] + + - title: "`split(regex; flags)`" + body: | + + For backwards compatibility, `split` splits on a string, not a regex. + + example: + - program: 'split(", *"; null)' + input: '"ab,cd, ef"' + output: ['"ab","cd","ef"'] + + + - title: "\\[Requires 1.5\\] `splits(regex)`, `splits(regex; flags)`" + body: | + + These provide the same results as their `split` counterparts, + but as a stream instead of an array. + + example: + - program: 'splits(", *")' + input: '("ab,cd", "ef, gh")' + output: ['"ab"', '"cd"', '"ef"', '"gh"'] + + - title: "\\[Requires 1.5\\] `sub(regex; tostring)` `sub(regex; string; flags)`" + body: | + + 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)". + + example: + - program: 'sub("^[^a-z]*(?[a-z]*).*")' + input: '"123abc456"' + output: '"ZabcZabc"' + + + - title: "\\[Requires 1.5\\] `gsub(regex; string)`, `gsub(regex; string; flags)`" + body: | + + `gsub` is like `sub` but all the non-overlapping occurrences of the regex are + replaced by the string, after interpolation. + + example: + - program: 'gsub("(?.)[^a]*"; "+\(.x)-")' + input: '"Abcabc"' + output: '"+A-+a-"' + + + - title: Advanced features + body: | + 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. + + entries: + - title: Variables + body: | + + 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. + + examples: + - program: '.bar as $x | .foo | . + $x' + input: '{"foo":10, "bar":200}' + output: ['210'] + - program: '. as $i|[(.*2|. as $i| $i), $i]' + input: '5' + output: ['[10,5]'] + - program: '. as [$a, $b, {c: $c}] | $a + $b + $c' + input: '[2, 3, {"c": 4, "d": 5}]' + output: ['9'] + - program: '.[] as [$a, $b] | {a: $a, b: $b}' + input: '[[0], [0, 1], [2, 1, 0]]' + output: ['{"a":0,"b":null}', '{"a":0,"b":1}', '{"a":2,"b":1}'] + + - title: 'Defining Functions' + body: | + + 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 some of the builtins + are defined). A function may take arguments: + + def map(f): [.[] | f]; + + Arguments are passed as filters, 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. + + 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. + + examples: + - program: 'def addvalue(f): . + [f]; map(addvalue(.[0]))' + input: '[[1,2],[10,20]]' + output: ['[[1,2,1], [10,20,10]]'] + - program: 'def addvalue(f): f as $x | map(. + $x); addvalue(.[0])' + input: '[[1,2],[10,20]]' + output: ['[[1,2,1,2], [10,20,1,2]]'] + + - title: Reduce + body: | + + 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) + + examples: + - program: 'reduce .[] as $item (0; . + $item)' + input: '[10,2,5,3]' + output: ['20'] + + - title: "`limit(n; exp)`" + body: | + + The `limit` function extracts up to `n` outputs from `exp`. + + examples: + - program: '[limit(3;.[])]' + input: '[0,1,2,3,4,5,6,7,8,9]' + output: ['[0,1,2]'] + + - title: "`first(expr)`, `last(expr)`, `nth(n; expr)`" + body: | + + 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`. + + examples: + - program: '[first(range(.)), last(range(.)), nth(./2; range(.))]' + input: '10' + output: ['[0,9,5]'] + + - title: "`first`, `last`, `nth(n)`" + body: | + + 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 `.`. + + examples: + - program: '[range(.)]|[first, last, nth(5)]' + input: '10' + output: ['[0,9,5]'] + + - title: "`foreach`" + body: | + + 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). + + examples: + - program: '[foreach .[] as $item + ([[],[]]; + if $item == null then [[],.[0]] else [(.[0] + [$item]),[]] end; + if $item == null then .[1] else empty end)]' + input: '[1,2,3,4,null,"a","b",null]' + output: ['[[1,2,3,4],["a","b"]]'] + + - title: Recursion + body: | + + 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; + + - title: Generators and iterators + body: | + + 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. + + examples: + - program: '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)' + input: 'null' + output: ['0', '3', '6', '9'] + - program: 'def while(cond; update): + def _while: + if cond then ., (update | _while) else empty end; + _while; + [while(.<100; .*2)]' + input: '1' + output: ['[1,2,4,8,16,32,64]'] + + - title: 'Math' + body: | + + 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 `.`. + + 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. + + - title: 'I/O' + body: | + + 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. + + One builtin provides minimal output capabilities, `debug`. + (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. + + entries: + - title: "`input`" + body: | + + Outputs one new input. + + - title: "`inputs`" + body: | + + Outputs all remaining inputs, one by one. + + This is primarily useful for reductions over a program's + inputs. + + - title: "`debug`" + body: | + + Causes a debug message based on the input value to be + produced. The jq executable wraps the input value with + `["DEBUG:", ]` and prints that and a newline on + stderr, compactly. This may change in the future. + + - title: "`input_filename`" + body: | + + 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. + + - title: "`input_line_number`" + body: | + + Returns the line number of the input currently being filtered. + + - title: 'Streaming' + body: | + + 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 `[, ]` (and a few other forms) as inputs. + + Several builtins are provided to make handling streams easier. + + The examples below use the the streamed form of `[0,[1]]`, which + is `[[0],0],[[1,0],1],[[1,0]],[[1]]`. + + Streaming forms include `[, ]` (to indicate any + scalar value, empty array, or empty object), and `[]` (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. + + entries: + - title: "`truncate_stream(stream_expression)`" + body: | + + Consumes a number as input and truncates the corresponding + number of path elements from the left of the outputs of the + given streaming expression. + + examples: + - program: '[1|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]])]' + input: '1' + output: ['[[[0],2],[[0]]]'] + + - title: "`fromstream(stream_expression)`" + body: | + + Outputs values corresponding to the stream expression's + outputs. + + examples: + - program: 'fromstream(1|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]]))' + input: 'null' + output: ['[2]'] + + - title: "`tostream`" + body: | + + The `tostream` builtin outputs the streamed form of its input. + + examples: + - program: '. as $dot|fromstream($dot|tostream)|.==$dot' + input: '[0,[1,{"a":1},{"b":2}]]' + output: ['true'] + + - title: Assignment + body: | + + Assignment works a little differently in jq than in most + programming languages. jq doesn't distinguish between references + to and copies of something - two objects or arrays are either + equal or not equal, without any further notion of being "the + same object" or "not the same object". + + If an object has two fields which are arrays, `.foo` and `.bar`, + and you append something to `.foo`, then `.bar` will not get + bigger. Even if you've just set `.bar = .foo`. If you're used to + programming in languages like Python, Java, Ruby, Javascript, + etc. then you can think of it as though jq does a full deep copy + of every object before it does the assignment (for performance, + it doesn't actually do that, but that's the general idea). + + All the assignment operators in jq have path expressions on the + left-hand side. + + entries: + - title: "`=`" + body: | + + The filter `.foo = 1` will take as input an object + and produce as output an object with the "foo" field set to + 1. There is no notion of "modifying" or "changing" something + in jq - all jq values are immutable. For instance, + + .foo = .bar | .foo.baz = 1 + + will not have the side-effect of setting .bar.baz to be set + to 1, as the similar-looking program in Javascript, Python, + Ruby or other languages would. Unlike these languages (but + like Haskell and some other functional languages), there is + no notion of two arrays or objects being "the same array" or + "the same object". They can be equal, or not equal, but if + we change one of them in no circumstances will the other + change behind our backs. + + This means that it's impossible to build circular values in + jq (such as an array whose first element is itself). This is + quite intentional, and ensures that anything a jq program + can produce can be represented in JSON. + + Note that the left-hand side of '=' refers to a value in `.`. + Thus `$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 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 below) do + not do this. + + Note too that `.a,.b=0` does not set `.a` and `.b`, but + `(.a,.b)=0` sets both. + + - title: "`|=`" + body: | + As well as the assignment operator '=', jq provides the "update" + operator '|=', which 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 |= .+1 will build an object with the "foo" + field set to the input's "foo" plus 1. + + 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}. The latter will set the "a" + field of the input to the "a" field's "b" field, producing {"a": 10}. + + 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 multiple values, only the last + one will be used. + + examples: + + - program: '(..|select(type=="boolean")) |= if . then 1 else 0 end' + input: '[true,false,[5,true,[true,[false]],false]]' + output: ['[1,0,[5,1,[1,[0]],0]]'] + + - title: "`+=`, `-=`, `*=`, `/=`, `%=`, `//=`" + body: | + + 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. + + examples: + - program: .foo += 1 + input: '{"foo": 42}' + output: ['{"foo": 43}'] + + - title: Complex assignments + body: | + 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."] + + - title: Modules + body: | + + 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. + + entries: + - title: "`import RelativePathString as NAME [];`" + body: | + + 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. + + - title: "`include RelativePathString [];`" + body: | + + 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. + + - title: "`import RelativePathString as $NAME [];`" + body: | + + Imports a JSON file found at the given path relative to a + directory in a search path. A ".json" suffix will be added to + the relative path string. The file's data will be available + as `$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. + + - title: "`module ;`" + body: | + + 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. + + - title: "`modulemeta`" + body: | + + 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. + diff --git a/docs/content/index/index.yml b/docs/content/index/index.yml index 6fb70428..14f5c84f 100644 --- a/docs/content/index/index.yml +++ b/docs/content/index/index.yml @@ -24,7 +24,7 @@ body3: | tail: | - Go read the [tutorial](tutorial/) for more, or the [manual](manual/) + Go read the [tutorial](/jq/tutorial/) for more, or the [manual](/jq/manual/) for *way* more. Ask questions on [stackoverflow](https://stackoverflow.com/) using the [jq @@ -33,24 +33,34 @@ tail: | [Freenode](https://webchat.freenode.net/). news: - - date: 2015-07-26 + - date: 15 August 2015 + body: | + + jq 1.5 released, including new datetime, math, and regexp functions, + try/catch syntax, array and object destructuring, a streaming parser, + and a module system. See installation options on the + [download](/jq/download/) page, and the + [release notes](https://github.com/stedolan/jq/releases/tag/jq-1.5) + for details. + + - date: 26 July 2015 body: | jq 1.5rc2 is available. Get it on the [releases](https://github.com/stedolan/jq/releases) page. - - date: 2015-01-01 + - date: 01 January 2015 body: | jq 1.5rc1 is available. Get it on the [releases](https://github.com/stedolan/jq/releases) page. - - date: 2014-06-08 + - date: 09 June 2014 body: | - jq 1.4 (finally) released! Get it on the [download](download/) page. + jq 1.4 (finally) released! Get it on the [download](/jq/download/) page. - - date: 2013-05-19 + - date: 19 May 2013 body: | jq 1.3 released. diff --git a/docs/templates/index.liquid b/docs/templates/index.liquid index 52f9de9c..03d75dfb 100644 --- a/docs/templates/index.liquid +++ b/docs/templates/index.liquid @@ -20,18 +20,13 @@