常用 linux jq 命令语法整理

向右看齐 2022-10-10 01:58 567阅读 0赞

### 常用 linux jq 命令语法整理 ###

<table> 
 <thead> 
 <tr> 
 <th>语法</th> 
 <th>json</th> 
 <th>命令</th> 
 <th>result str</th> 
 <th>说明</th> 
 </tr> 
 </thead> 
 <tbody> 
 <tr> 
 <td>.</td> 
 <td>“Hello, world!”</td> 
 <td>jq ‘.’</td> 
 <td>“Hello, world!”</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“foo”: 42, “bar”: “less interesting data”}</td> 
 <td>jq ‘.foo’</td> 
 <td>42</td> 
 <td>返回对象foo key 值</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“notfoo”: true, “alsonotfoo”: false}</td> 
 <td>jq ‘.foo’</td> 
 <td>null</td> 
 <td>对象key不存在，返回null</td> 
 </tr> 
 <tr> 
 <td>.[]</td> 
 <td>[1,2,3]</td> 
 <td>jq ‘.[]’</td> 
 <td>1 2 3</td> 
 <td>元素遍历</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“a”: 1, “b”: 2}</td> 
 <td>jq ‘.[]’</td> 
 <td>1 2</td> 
 <td>key 对值遍历</td> 
 </tr> 
 <tr> 
 <td>.[&lt;string&gt;]</td> 
 <td>{“foo”: 42}</td> 
 <td>jq .[“foo”]</td> 
 <td>42</td> 
 <td>获取key 对应值</td> 
 </tr> 
 <tr> 
 <td>.[&lt;value&gt;]</td> 
 <td>[{“name”:“JSON”, “good”:true}, {“name”:“XML”, “good”:false}]</td> 
 <td>jq ‘.[0]’</td> 
 <td>{“name”:“JSON”, “good”:true}</td> 
 <td>返回1下标元素</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[1,2,3]</td> 
 <td>jq ‘.[-2]’</td> 
 <td>2</td> 
 <td>返回倒数两个位置元素</td> 
 </tr> 
 <tr> 
 <td>.[start:end]</td> 
 <td>[“a”,“b”,“c”,“d”,“e”]</td> 
 <td>jq ‘.[2:4]’</td> 
 <td>[“c”, “d”]</td> 
 <td>下标开始到下标结束的元素</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>“abcdefghi”</td> 
 <td>jq ‘.[2:4]’</td> 
 <td>“cd”</td> 
 <td>下标开始到下标结束的字符</td> 
 </tr> 
 <tr> 
 <td>.[:end]</td> 
 <td>[“a”,“b”,“c”,“d”,“e”]</td> 
 <td>jq ‘.[:3]’</td> 
 <td>[“a”, “b”, “c”]</td> 
 <td>首个元素到指定下标元素之间的元素</td> 
 </tr> 
 <tr> 
 <td>.[start:]</td> 
 <td>[“a”,“b”,“c”,“d”,“e”]</td> 
 <td>jq ‘.[-2:]’</td> 
 <td>[“d”, “e”]</td> 
 <td>指定下标开始到未元素之间的元素</td> 
 </tr> 
 <tr> 
 <td>,</td> 
 <td>{“foo”: 42, “bar”: “something else”, “baz”: true}</td> 
 <td>jq ‘.foo, .bar’</td> 
 <td>42, “something else”</td> 
 <td>获取多个key值</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“user”:“stedolan”, “projects”: [“jq”, “wikiflow”]}</td> 
 <td>jq ‘.user, .projects[]’</td> 
 <td>“stedolan”, “jq”, “wikiflow”</td> 
 <td>b取多个元素的值</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[“a”,“b”,“c”,“d”,“e”]</td> 
 <td>jq ‘.[4,2]’</td> 
 <td>“e”, “c”</td> 
 <td>取4 和 2 下标元素</td> 
 </tr> 
 <tr> 
 <td>|</td> 
 <td>[{“name”:“JSON”, “good”:true}, {“name”:“XML”, “good”:false}]</td> 
 <td>jq ‘.[] | .name’</td> 
 <td>“JSON”, “XML”</td> 
 <td>管道</td> 
 </tr> 
 <tr> 
 <td>[]</td> 
 <td>{“user”:“stedolan”, “projects”: [“jq”, “wikiflow”]}</td> 
 <td>jq ‘[.user, .projects[]]’</td> 
 <td>[“stedolan”, “jq”, “wikiflow”]</td> 
 <td>元素值组成新数组</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[1, 2, 3]</td> 
 <td>jq ‘[ .[] | . * 2]’</td> 
 <td>[2, 4, 6]</td> 
 <td>元素值组成新数组</td> 
 </tr> 
 <tr> 
 <td>{}</td> 
 <td>[{“user”:“stedolan”, “title”: “JQ Primer”}]</td> 
 <td>jq ‘.[] | {user, title}’</td> 
 <td>{“user”:“stedolan”, “title”: “JQ Primer”}</td> 
 <td>组成对象(使用原key名)</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[{“user”:“stedolan”, “title”: “JQ Primer”}]</td> 
 <td>jq ‘.[] | {user1: .user, title: .title}’</td> 
 <td>{“user1”:“stedolan”, “title”: “JQ Primer”}</td> 
 <td>组成对象(改变key名)</td> 
 </tr> 
 <tr> 
 <td>+</td> 
 <td>{“a”: 7}</td> 
 <td>jq ‘.a + 1’</td> 
 <td>8</td> 
 <td>算术运算符</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“a”: [1,2], “b”: [3,4]}</td> 
 <td>jq ‘.a + .b’</td> 
 <td>[1,2,3,4]</td> 
 <td>数组元素合并</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td>jq ‘{a: 1} + {b: 2} + {c: 3} + {a: 42}’</td> 
 <td>{“a”: 42, “b”: 2, “c”: 3}</td> 
 <td>合并属性</td> 
 </tr> 
 <tr> 
 <td>-</td> 
 <td>{“a”:3}</td> 
 <td>jq ‘4 - .a’</td> 
 <td>1</td> 
 <td>算术运算符</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[“xml”, “yaml”, “json”]</td> 
 <td>jq ‘. - [“xml”, “yaml”]’</td> 
 <td>[“json”]</td> 
 <td>删除指定数组内元素</td> 
 </tr> 
 <tr> 
 <td>/</td> 
 <td>5</td> 
 <td>jq '10 / . ’</td> 
 <td>2</td> 
 <td>算术运算符</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>“a,b,c,d,e”</td> 
 <td>jq ‘. / “,”’</td> 
 <td>[“a”,“b”,“c”,“d”,“e”]</td> 
 <td>字符串分隔成数组</td> 
 </tr> 
 <tr> 
 <td>length</td> 
 <td>[1,2]</td> 
 <td>jq ‘. | length’</td> 
 <td>2</td> 
 <td>数组元素个数</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>“string”</td> 
 <td>jq ‘. | length’</td> 
 <td>6</td> 
 <td>string 的长度</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“a”:2}</td> 
 <td>jq ‘. | length’</td> 
 <td>1</td> 
 <td>对象key个数</td> 
 </tr> 
 <tr> 
 <td>keys</td> 
 <td>[“a”,“b”,“c”]</td> 
 <td>jq ’ . | keys’</td> 
 <td>[0,1,2]</td> 
 <td>数组下标数组</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“abc”: 1, “abcd”: 2, “Foo”: 3}</td> 
 <td>jq ’ . | keys’</td> 
 <td>[“Foo”, “abc”, “abcd”]</td> 
 <td>kye数组</td> 
 </tr> 
 <tr> 
 <td>has(key)</td> 
 <td>{“abc”: 1, “abcd”: 2, “Foo”: 3}</td> 
 <td>jq ‘. | has(“abc”)’</td> 
 <td>true</td> 
 <td>是否包含key</td> 
 </tr> 
 <tr> 
 <td>map(x)</td> 
 <td>[1,2,3]</td> 
 <td>jq ‘map(.+1)’</td> 
 <td>[2,3,4]</td> 
 <td>元素遍历</td> 
 </tr> 
 <tr> 
 <td>map_values(x)</td> 
 <td>{“a”: 1, “b”: 2, “c”: 3}</td> 
 <td>jq ‘map_values(.+1)’</td> 
 <td>{“a”: 2, “b”: 3, “c”: 4}</td> 
 <td>对象值遍历</td> 
 </tr> 
 <tr> 
 <td>del(path_expression)</td> 
 <td>{“foo”: 42, “bar”: 9001, “baz”: 42}</td> 
 <td>jq ‘del(.foo)’</td> 
 <td>{“bar”: 9001, “baz”: 42}</td> 
 <td>删除key</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[“foo”, “bar”, “baz”]</td> 
 <td>jq ‘del(.[1, 2])’</td> 
 <td>[“foo”]</td> 
 <td>删除元素</td> 
 </tr> 
 <tr> 
 <td>getpath(PATHS)</td> 
 <td>{“a”:{“b”:0, “c”:1}}</td> 
 <td>jq ‘[getpath([“a”,“b”], [“a”,“c”])]’</td> 
 <td>[0, 1]</td> 
 <td>获取指定值</td> 
 </tr> 
 <tr> 
 <td>setpath(PATHS; VALUE)</td> 
 <td>{“a”:{“b”:0}}</td> 
 <td>jq ‘setpath([“a”,“b”]; 1)’</td> 
 <td>{“a”: {“b”: 1}}</td> 
 <td>设置指定值</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td>jq ‘setpath([0,“a”]; 1)’</td> 
 <td>[{“a”:1}]</td> 
 <td>设置指定值</td> 
 </tr> 
 <tr> 
 <td>select(boolean_expression)</td> 
 <td>[1,5,3,0,7]</td> 
 <td>jq ‘map(select(. &gt;= 2))’</td> 
 <td>[5,3,7]</td> 
 <td>select</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[{“id”: “first”, “val”: 1}, {“id”: “second”, “val”: 2}]</td> 
 <td>jq ‘.[] | select(.id == “second”)’</td> 
 <td>{“id”: “second”, “val”: 2}</td> 
 <td>select</td> 
 </tr> 
 <tr> 
 <td>arrays, objects, iterables, booleans, numbers, normals, finites, strings, nulls, values, scalars</td> 
 <td>[[],{},1,“foo”,null,true,false]</td> 
 <td>jq ‘.[] | numbers’</td> 
 <td>1</td> 
 <td>从数组中取指定类型值</td> 
 </tr> 
 <tr> 
 <td>add</td> 
 <td>[“a”,“b”,“c”]</td> 
 <td>jq ‘add’</td> 
 <td>“abc”</td> 
 <td>字符串元素拼接</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[1, 2, 3]</td> 
 <td>jq ‘add’</td> 
 <td>6</td> 
 <td>sum</td> 
 </tr> 
 <tr> 
 <td>any, any(condition), any(generator; condition)</td> 
 <td>[true, false]</td> 
 <td>jq ‘any’</td> 
 <td>true</td> 
 <td>有一个元素是true返回true</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[false, false]</td> 
 <td>jq ‘any’</td> 
 <td>false</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[]</td> 
 <td>jq ‘any’</td> 
 <td>false</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[1,2,3]</td> 
 <td>jq ‘any(. &gt; 1)’</td> 
 <td>true</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>all, all(condition), all(generator; condition)</td> 
 <td>[true, false]</td> 
 <td>jq ‘all’</td> 
 <td>false</td> 
 <td>所有元素是true返回true</td> 
 </tr> 
 <tr> 
 <td>range(upto), range(from;upto) range(from;upto;by)</td> 
 <td></td> 
 <td>jq ‘[range(4)]’</td> 
 <td>[0,1,2,3]</td> 
 <td>步进</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td>jq ‘range(2;4)’</td> 
 <td>2, 3</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td>jq ‘[range(2;4)]’</td> 
 <td>[2,3]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td>jq ‘[range(0;10;3)]’</td> 
 <td>[0,3,6,9]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td>jq ‘[range(0;-5;-1)]’</td> 
 <td>[0,-1,-2,-3,-4]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>floor</td> 
 <td>3.14159</td> 
 <td>jq ‘floor’</td> 
 <td>3</td> 
 <td>取整</td> 
 </tr> 
 <tr> 
 <td>sqrt</td> 
 <td>9</td> 
 <td>jq ‘sqrt’</td> 
 <td>3</td> 
 <td>开根</td> 
 </tr> 
 <tr> 
 <td>tonumber</td> 
 <td>[1, “1”]</td> 
 <td>jq ‘.[] | tonumber’</td> 
 <td>1, 1</td> 
 <td>转数字</td> 
 </tr> 
 <tr> 
 <td>tostring</td> 
 <td>[1, “1”, [1]]</td> 
 <td>jq ‘.[] | tostring’</td> 
 <td>[“1”, “1”, “[1]”]</td> 
 <td>转json 字符串</td> 
 </tr> 
 <tr> 
 <td>type</td> 
 <td>[0, false, [], {}, null, “hello”]</td> 
 <td>jq ‘map(type)’</td> 
 <td>[“number”, “boolean”, “array”, “object”, “null”, “string”]</td> 
 <td>查看类型</td> 
 </tr> 
 <tr> 
 <td>sort, sort_by(path_expression)</td> 
 <td>[8,3,null,6]</td> 
 <td>jq ‘sort’</td> 
 <td>[null,3,6,8]</td> 
 <td>order by</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[{“foo”:4, “bar”:10}, {“foo”:3, “bar”:100}, {“foo”:2, “bar”:1}]</td> 
 <td>jq ‘sort_by(.foo)’</td> 
 <td>[{“foo”:2, “bar”:1}, {“foo”:3, “bar”:100}, {“foo”:4, “bar”:10}]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>group_by(path_expression)</td> 
 <td>[{“foo”:1, “bar”:10}, {“foo”:3, “bar”:100}, {“foo”:1, “bar”:1}]</td> 
 <td>jq ‘group_by(.foo)’</td> 
 <td>[[{“foo”:1, “bar”:10}, {“foo”:1, “bar”:1}], [{“foo”:3, “bar”:100}]]</td> 
 <td>聚合函数group by</td> 
 </tr> 
 <tr> 
 <td>min, max, min_by(path_exp), max_by(path_exp)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>unique, unique_by(path_exp)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>reverse</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>contains(element)</td> 
 <td>“foobar”</td> 
 <td>jq ‘contains(“bar”)’</td> 
 <td>true</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[“foobar”, “foobaz”, “blarp”]</td> 
 <td>jq ‘contains([“baz”, “bar”])’</td> 
 <td>true</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[“foobar”, “foobaz”, “blarp”]</td> 
 <td>jq ‘contains([“bazzzzz”, “bar”])’</td> 
 <td>false</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“foo”: 12, “bar”:[1,2,{“barp”:12, “blip”:13}]}</td> 
 <td>jq ‘contains({foo: 12, bar: [{barp: 12}]})’</td> 
 <td>true</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“foo”: 12, “bar”:[1,2,{“barp”:12, “blip”:13}]}</td> 
 <td>jq ‘contains({foo: 12, bar: [{barp: 15}]})’</td> 
 <td>false</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>indices(s)</td> 
 <td>“a,b, cd, efg, hijk”</td> 
 <td>jq ‘indices(", ")’</td> 
 <td>[3,7,12]</td> 
 <td>返回出现元素下标位置集合</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[0,1,2,1,3,1,4]</td> 
 <td>jq ‘indices(1)’</td> 
 <td>[1,3,5]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[0,1,2,3,1,4,2,5,1,2,6,7]</td> 
 <td>jq ‘indices([1,2])’</td> 
 <td>[1,8]</td> 
 <td>s可以输入为数组</td> 
 </tr> 
 <tr> 
 <td>index(s), rindex(s)</td> 
 <td>“a,b, cd, efg, hijk”</td> 
 <td>jq ‘index(", ")’</td> 
 <td>3</td> 
 <td>indexof</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>“a,b, cd, efg, hijk”</td> 
 <td>jq 'rindex(", ")</td> 
 <td>12</td> 
 <td>lastIndexOf</td> 
 </tr> 
 <tr> 
 <td>inside</td> 
 <td>“bar”</td> 
 <td>jq ‘inside(“foobar”)’</td> 
 <td>true</td> 
 <td>包含元素</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>{“foo”: 12, “bar”: [{“barp”: 15}]}</td> 
 <td>jq ‘inside({“foo”: 12, “bar”:[1,2,{“barp”:12, “blip”:13}]})’</td> 
 <td>false</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>startswith(str)</td> 
 <td>[“fo”, “foo”, “barfoo”, “foobar”, “barfoob”]</td> 
 <td>jq ‘[.[] | startswith(“foo”)]’</td> 
 <td>[false, true, false, true, false]</td> 
 <td>开始于</td> 
 </tr> 
 <tr> 
 <td>endswith(str)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td>结束于</td> 
 </tr> 
 <tr> 
 <td>combinations, combinations(n)</td> 
 <td>[[1,2], [3, 4]]</td> 
 <td>jq ‘combinations’</td> 
 <td>[1, 3], [1, 4], [2, 3], [2, 4]</td> 
 <td>组合笛卡尔积</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td>[0, 1]</td> 
 <td>jq ‘combinations(2)’</td> 
 <td>[0, 0], [0, 1], [1, 0], [1, 1]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>ltrimstr(str)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>rtrimstr(str)</td> 
 <td>[“fo”, “foo”, “barfoo”, “foobar”, “afoo”]</td> 
 <td>jq ‘[.[] | ltrimstr(“foo”)]’</td> 
 <td>[“fo”,"",“barfoo”,“bar”,“afoo”]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>split(str)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td>split</td> 
 </tr> 
 <tr> 
 <td>join(str)</td> 
 <td>[“a”,1,2.3,true,null,false]</td> 
 <td>jq ‘join(" ")’</td> 
 <td>“a 1 2.3 true false”</td> 
 <td>转string指定分隔符</td> 
 </tr> 
 <tr> 
 <td>while(cond; update)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>until(cond; next)</td> 
 <td>4</td> 
 <td>jq ‘[.,1] | until(.[0] &lt; 1; [.[0] - 1, .[1] * .[0]]) | .[1]’</td> 
 <td>24 (4*3*2*1)</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>foreach</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>tojson</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>Format strings and escaping</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@text</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@json</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@html</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@uri</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@csv</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@tsv</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@sh</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>@base64</td> 
 <td>“This is a message”</td> 
 <td>jq '@base64</td> 
 <td>“VGhpcyBpcyBhIG1lc3NhZ2U=”</td> 
 <td>加密</td> 
 </tr> 
 <tr> 
 <td>@base64d</td> 
 <td>###</td> 
 <td>###</td> 
 <td></td> 
 <td>解密</td> 
 </tr> 
 <tr> 
 <td>==, != &gt;, &gt;=, &lt;=, &lt; and/or/not</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>+=, -=, *=, /=, %=, //=</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>if A then elif B else C end</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>//</td> 
 <td>{}</td> 
 <td>jq ‘.foo // 42’</td> 
 <td>42</td> 
 <td>提供默认值</td> 
 </tr> 
 <tr> 
 <td>isempty(exp)</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>limit(n; exp)</td> 
 <td>[0,1,2,3,4,5,6,7,8,9]</td> 
 <td>jq ‘[limit(3;.[])]’</td> 
 <td>[0,1,2]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>first(expr), last(expr), nth(n; expr)</td> 
 <td>10</td> 
 <td>jq ‘[first(range(.)), last(range(.)), nth(./2; range(.))]’</td> 
 <td>[0,9,5]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>first, last, nth(n)</td> 
 <td>10</td> 
 <td>jq ‘[range(.)] | [first, last, nth(5)]’</td> 
 <td>[0,9,5]</td> 
 <td></td> 
 </tr> 
 <tr> 
 <td>?</td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td>忽略异常</td> 
 </tr> 
 <tr> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 <td></td> 
 </tr> 
 </tbody> 
</table>