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简介

如果说要给Linux文本三剑客(grep、sed、awk)添加一员的话，我觉得应该是jq命令，因为jq命令是用来处理json数据的工具，而现如今json几乎无所不在！

网上的jq命令分享文章也不少，但大多介绍得非常浅，jq的强大之处完全没有介绍出来，所以就有了这篇文章，安利一下jq这个命令。

基本用法格式化

# jq默认的格式化输出$ echo -n '{"id":1, "name":"zhangsan", "score":[75, 85, 90]}'|jq .{  "id": 1,  "name": "zhangsan",  "score": [    75,    85,    90  ]}# -c选项则是压缩到1行输出$ jq -c . <<eof{  "id": 1,  "name": "zhangsan",  "score": [    75,    85,    90  ]}eof{"id":1,"name":"zhangsan","score":[75,85,90]}

# 获取id字段$ echo -n '{"id":1, "name":"zhangsan", "score":[75, 85, 90]}'|jq '.id'1# 获取name字段$ echo -n '{"id":1, "name":"zhangsan", "score":[75, 85, 90]}'|jq '.name'"zhangsan"# 获取name字段，-r 解开字符串引号$ echo -n '{"id":1, "name":"zhangsan", "score":[75, 85, 90]}'|jq -r '.name'zhangsan# 多层属性值获取$ echo -n '{"id":1, "name":"zhangsan", "attr":{"height":1.78,"weight":"60kg"}}'|jq '.attr.height'1.78# 获取数组中的值$ echo -n '{"id":1, "name":"zhangsan", "score":[75, 85, 90]}'|jq -r '.score[0]'75$ echo -n '[75, 85, 90]'|jq -r '.[0]'75# 数组截取$ echo -n '[75, 85, 90]'|jq -r '.[1:3]'[  85,  90]# []展开数组$ echo -n '[75, 85, 90]'|jq '.[]'758590# ..展开所有结构$ echo -n '{"id":1, "name":"zhangsan", "score":[75, 85, 90]}'|jq -c '..'{"id":1,"name":"zhangsan","score":[75,85,90]}1"zhangsan"[75,85,90]758590# 从非对象类型中提取字段，会报错$ echo -n '{"id":1, "name":"zhangsan", "attr":{"height":1.78,"weight":"60kg"}}'|jq '.name.alias'jq: error (at <stdin>:0): Cannot index string with string "alias"# 使用?号可以避免这种报错$ echo -n '{"id":1, "name":"zhangsan", "attr":{"height":1.78,"weight":"60kg"}}'|jq '.name.alias?'# //符号用于，当前面的表达式取不到值时，执行后面的表达式$ echo -n '{"id":1, "name":"zhangsan", "attr":{"height":1.78,"weight":"60kg"}}'|jq '.alias//.name'"zhangsan"

# 管道可以将值从前一个命令传送到后一个命令$ echo -n '{"id":1, "name":"zhangsan", "attr":{"height":1.78,"weight":"60kg"}}'|jq '.attr|.height'1.78# jq中做一些基础运算也是可以的$ echo -n '{"id":1, "name":"zhangsan", "attr":{"height":1.78,"weight":"60kg"}}'|jq '.attr|.height*100|tostring + "cm"'"178cm"# 逗号使得可以执行多个jq表达式，使得一个输入可计算出多个输出结果$ echo 1 | jq '., ., .'111# 括号用于提升表达式的优先级，如下：逗号优先级低于算术运算$ $ echo '1'|jq '.+1, .*2'22$ echo '1'|jq '(.+1, .)*2'42# 管道优先级低于逗号$ echo '1'|jq '., .|tostring'"1""1"$ echo '1'|jq '., (.|tostring)'1"1"

表面上jq是用来处理json数据的，但实际上jq能处理的是任何json基础元素所形成的流，如integer、string、bool、null、object、array等，jq执行过程大致如下：

jq从流中获取一个json元素jq执行表达式，表达式生成新的json元素jq将新的json元素打印输出

可以看看这些示例，如下：

# 这里jq实际上将1 2 3 4当作4个integer元素，每找到一个元素就执行+1操作# jq实际上是流式处理的，1 2 3 4可以看成流中的4个元素$ echo '1 2 3 4'|jq '. + 1'2345# 流中的元素不需要是同种类型，只要是完整的json元素即可$ jq '"<" + tostring + ">"' <<eof1"zhangsan"true{"id":1}[75, 80, 85]eof"<1>""<zhangsan>""<true>""<{\"id\":1}>""<[75,80,85]>"# -R选项可用于将读取到的json元素，都当作字符串对待$ seq 4|jq -R '.'"1""2""3""4"# -s选项将从流中读取到的所有json元素，变成一个json数组元素  # 这里理解为jq从流中只取到了1个json元素，这个json元素的类型是数组$ seq 4|jq -s .[  1,  2,  3,  4]

jq支持 + - * / % 运算，对于+号，如果是字符串类型，则是做字符串拼接，如下：

# 做加减乘除运算$ echo 1|jq '.+1, .-1, .*2, ./2, .%2'2020.51# 赋值运算$ echo -n '{"id":1,"name":"zhangsan","age":"17","score":"75"}'|jq '.id=2' -c{"id":2,"name":"zhangsan","age":"17","score":"75"}

jq可以很方便的将其它数据，转化为json对象或数组，如下：

# 使用[]构造数组元素，-n告诉jq没有输入数据，直接执行表达式并生成输出数据$ jq -n '[1,2,3,4]' -c[1,2,3,4]$ cat data.txtid  name      age  score1   zhangsan  17   752   lisi      16   803   wangwu    18   854   zhaoliu   18   90# 每行分割成数组，[]构造新的数组输出$ tail -n+2 data.txt|jq -R '[splits("\\s+")]' -c["1","zhangsan","17","75"]["2","lisi","16","80"]["3","wangwu","18","85"]["4","zhaoliu","18","90"]$ jq -n '{id:1, name:"zhangsan"}' -c{"id":1,"name":"zhangsan"}# 每行转换为对象，{}构造新的对象格式输出$ tail -n+2 data.txt|jq -R '[splits("\\s+")] | {id:.[0]|tonumber, name:.[1], age:.[2], score:.[3]}' -c{"id":1,"name":"zhangsan","age":"17","score":"75"}{"id":2,"name":"lisi","age":"16","score":"80"}{"id":3,"name":"wangwu","age":"18","score":"85"}{"id":4,"name":"zhaoliu","age":"18","score":"90"}# \()字符串占位变量替换$ cat data.json{"id":1,"name":"zhangsan","age":"17","score":"75"}{"id":2,"name":"lisi","age":"16","score":"80"}{"id":3,"name":"wangwu","age":"18","score":"85"}{"id":4,"name":"zhaoliu","age":"18","score":"90"}$ cat data.json |jq '"id:\(.id),name:\(.name),age:\(.age),score:\(.score)"' -rid:1,name:zhangsan,age:17,score:75id:2,name:lisi,age:16,score:80id:3,name:wangwu,age:18,score:85id:4,name:zhaoliu,age:18,score:90

# has函数，检测对象是否包含key$ echo -n '{"id":1,"name":"zhangsan","age":"17","score":"75"}'|jq 'has("id")'true# del函数，删除某个属性$ echo -n '{"id":1,"name":"zhangsan","age":"17","score":"75"}'|jq 'del(.id)' -c{"name":"zhangsan","age":"17","score":"75"}# map函数，对数组中每个元素执行表达式计算，计算结果组织成新数组$ seq 4|jq -s 'map(. * 2)' -c[2,4,6,8]# 上面map函数写法，其实等价于这个写法$ seq 4|jq -s '[.[]|.*2]' -c[2,4,6,8]# keys函数，列出对象属性$ echo -n '{"id":1,"name":"zhangsan","age":"17","score":"75"}'|jq 'keys' -c["age","id","name","score"]# to_entries函数，列出对象键值对$ echo -n '{"id":1,"name":"zhangsan","age":"17","score":"75"}'|jq 'to_entries' -c[{"key":"id","value":1},{"key":"name","value":"zhangsan"},{"key":"age","value":"17"},{"key":"score","value":"75"}]# length函数，计算数组或字符串长度$ jq -n '[1,2,3,4]|length'4# add函数，计算数组中数值之和$ seq 4|jq -s 'add'10# tostring与tonumber，类型转换$ seq 4|jq 'tostring|tonumber'1234# type函数，获取元素类型$ jq 'type' <<eof1"zhangsan"truenull{"id":1}[75, 80, 85]eof"number""string""boolean""null""object""array"

$ cat data.json{"id":1,"name":"zhangsan","sex": 0, "age":"17","score":"75"}{"id":2,"name":"lisi","sex": 1, "age":"16","score":"80"}{"id":3,"name":"wangwu","sex": 0, "age":"18","score":"85"}{"id":4,"name":"zhaoliu","sex": 0, "age":"18","score":"90"}# select函数用于过滤，类似SQL中的where$ cat data.json |jq 'select( (.id>1) and (.age|IN("16","17","18")) and (.name != "lisi") or (has("attr")|not) and (.score|tonumber >= 90) )' -c{"id":3,"name":"wangwu","sex":0,"age":"18","score":"85"}{"id":4,"name":"zhaoliu","sex":0,"age":"18","score":"90"}# 有一些简化的过滤函数，如arrays, objects, iterables, booleans, numbers, normals, finites, strings, nulls, values, scalars# 它们根据类型过滤，如objects过滤出对象，values过滤出非null值等$ jq -c 'objects' <<eof1"zhangsan"truenull{"id":1}[75, 80, 85]eof{"id":1}$ jq -c 'values' <<eof1"zhangsan"truenull{"id":1}[75, 80, 85]eof1"zhangsan"true{"id":1}[75,80,85]# 选择出id与name字段，类似SQL中的select id,name$ cat data.json|jq -s 'map({id,name})[]' -c{"id":1,"name":"zhangsan"}{"id":2,"name":"lisi"}{"id":3,"name":"wangwu"}{"id":4,"name":"zhaoliu"}# 提取前2行，类似SQL中的limit 2$ cat data.json|jq -s 'limit(2; map({id,name})[])' -c{"id":1,"name":"zhangsan"}{"id":2,"name":"lisi"}# 按照age、id排序，类似SQL中的order by age,id$ cat data.json|jq -s 'sort_by((.age|tonumber), .id)[]' -c{"id":2,"name":"lisi","sex":1,"age":"16","score":"80"}{"id":1,"name":"zhangsan","sex":0,"age":"17","score":"75"}{"id":3,"name":"wangwu","sex":0,"age":"18","score":"85"}{"id":4,"name":"zhaoliu","sex":0,"age":"18","score":"90"}# 根据sex与age分组，并每组聚合计算count(*)、avg(score)、max(id)$ cat data.json |jq -s 'group_by(.sex, .age)[]' -c[{"id":1,"name":"zhangsan","sex":0,"age":"17","score":"75"}][{"id":3,"name":"wangwu","sex":0,"age":"18","score":"85"},{"id":4,"name":"zhaoliu","sex":0,"age":"18","score":"90"}][{"id":2,"name":"lisi","sex":1,"age":"16","score":"80"}]$ cat data.json |jq -s 'group_by(.sex, .age)[]|{sex:.[0].sex, age:.[0].age, count:length, avg_score:map(.score|tonumber)|(add/length), scores:map(.score)|join(","), max_id:map(.id)|max }' -c                 {"sex":0,"age":"17","count":1,"avg_score":75,"scores":"75","max_id":1}{"sex":0,"age":"18","count":2,"avg_score":87.5,"scores":"85,90","max_id":4}{"sex":1,"age":"16","count":1,"avg_score":80,"scores":"80","max_id":2}

# contains函数，判断是否包含，实际也可用于判断数组是否包含某个元素$ echo hello | jq -R 'contains("he")'true# 判断是否以he开头$ echo hello | jq -R 'startswith("he")'true# 判断是否以llo结尾$ echo hello | jq -R 'endswith("llo")'true# 去掉起始空格$ echo ' hello '|jq -R 'ltrimstr(" ")|rtrimstr(" ")'"hello"# 大小写转换$ echo hello|jq -R 'ascii_upcase'"HELLO"$ echo HELLO|jq -R 'ascii_downcase'"hello"# 字符串数组，通过逗号拼接成一个字符串$ seq 4|jq -s 'map(tostring)|join(",")'"1,2,3,4"# json字符串转换为json对象$ echo -n '{"id":1,"name":"zhangsan","age":"17","attr":"{\"weight\":56,\"height\":178}"}'|jq '.attr = (.attr|fromjson)' -c{"id":1,"name":"zhangsan","age":"17","attr":{"weight":56,"height":178}}# json对象转换为json字符串$ echo -n '{"id":1,"name":"zhangsan","age":"17","attr":{"weight":56,"height":178}}'|jq '.attr = (.attr|tojson)'{  "id": 1,  "name": "zhangsan",  "age": "17",  "attr": "{\"weight\":56,\"height\":178}"}$ cat data.txtid:1,name:zhangsan,age:17,score:75id:2,name:lisi,age:16,score:80id:3,name:wangwu,age:18,score:85id:4,name:zhaoliu,age:18,score:90# 正则表达式过滤，jq使用的是PCRE$ cat data.txt|jq -R 'select(test("id:\\d+,name:\\w+,age:\\d+,score:8\\d+"))' -rid:2,name:lisi,age:16,score:80id:3,name:wangwu,age:18,score:85# 正则拆分字符串$ cat data.txt|jq -R '[splits(",")]' -cr["id:1","name:zhangsan","age:17","score:75"]["id:2","name:lisi","age:16","score:80"]["id:3","name:wangwu","age:18","score:85"]["id:4","name:zhaoliu","age:18","score:90"]# 正则替换字符串$ cat data.txt |jq -R 'gsub("name"; "nick")' -rid:1,nick:zhangsan,age:17,score:75id:2,nick:lisi,age:16,score:80id:3,nick:wangwu,age:18,score:85id:4,nick:zhaoliu,age:18,score:90# 正则表达式捕获数据$ cat data.txt|jq -R 'match("id:(?<id>\\d+),name:(?<name>\\w+),age:\\d+,score:8\\d+")' -cr{"offset":0,"length":30,"string":"id:2,name:lisi,age:16,score:80","captures":[{"offset":3,"length":1,"string":"2","name":"id"},{"offset":10,"length":4,"string":"lisi","name":"name"}]}{"offset":0,"length":32,"string":"id:3,name:wangwu,age:18,score:85","captures":[{"offset":3,"length":1,"string":"3","name":"id"},{"offset":10,"length":6,"string":"wangwu","name":"name"}]}# capture命名捕获，生成key是捕获组名称，value是捕获值的对象$ cat data.txt|jq -R 'capture("id:(?<id>\\d+),name:(?<name>\\w+),age:\\d+,score:8\\d+")' -rc{"id":"2","name":"lisi"}{"id":"3","name":"wangwu"}# 正则扫描输入字符串$ cat data.txt|jq -R '[scan("\\w+:\\w+")]' -rc["id:1","name:zhangsan","age:17","score:75"]["id:2","name:lisi","age:16","score:80"]["id:3","name:wangwu","age:18","score:85"]["id:4","name:zhaoliu","age:18","score:90"]

# 当前时间缀$ jq -n 'now'1653820640.939947# 将时间缀转换为0时区的分解时间(broken down time)，形式为 年 月 日 时 分 秒 dayOfWeek dayOfYear$ jq -n 'now|gmtime' -c[2022,4,29,10,45,5.466768980026245,0,148]# 将时间缀转换为本地时区的分解时间(broken down time)$ jq -n 'now|localtime' -c[2022,4,29,18,46,5.386353015899658,0,148]# 分解时间转换为时间串$ jq -n 'now|localtime|strftime("%Y-%m-%dT%H:%M:%S")' -c"2022-05-29T18:50:33"# 与上面等效$ jq -n 'now|strflocaltime("%Y-%m-%dT%H:%M:%SZ")'"2022-05-29T19:00:40Z"# 时间串解析为分解时间$ date +%FT%T|jq -R 'strptime("%Y-%m-%dT%H:%M:%S")' -c[2022,4,29,18,51,27,0,148]# 分解时间转换为时间缀$ date +%FT%T|jq -R 'strptime("%Y-%m-%dT%H:%M:%S")|mktime'1653850310

实际上jq是一门脚本语言，它也支持变量、分支结构、循环结构与自定义函数，如下：

$ cat data.json{"id":1,"name":"zhangsan","sex": 0, "age":"17","score":"75"}{"id":2,"name":"lisi","sex": 1, "age":"16","score":"80"}{"id":3,"name":"wangwu","sex": 0, "age":"18","score":"85"}{"id":4,"name":"zhaoliu","sex": 0, "age":"18","score":"90"}# 单变量定义$ cat data.json| jq '.id as $id|$id'1234# 对象展开式变量定义$ cat data.json |jq '. as {id:$id,name:$name}|"id:\($id),name:\($name)"'"id:1,name:zhangsan""id:2,name:lisi""id:3,name:wangwu""id:4,name:zhaoliu"$ cat data.json["1","zhangsan","17","75"]["2","lisi","16","80"]["3","wangwu","18","85"]["4","zhaoliu","18","90"]# 数组展开式变量定义$ cat data.json|jq '. as [$id,$name]|"id:\($id),name:\($name)"'"id:1,name:zhangsan""id:2,name:lisi""id:3,name:wangwu""id:4,name:zhaoliu"# 分支结构$ cat data.json|jq '. as [$id,$name]|if ($id>"1") then "id:\($id),name:\($name)" else empty end'"id:2,name:lisi""id:3,name:wangwu""id:4,name:zhaoliu"# 循环结构，第一个表达式条件满足时，执行只每二个表达式# 循环结构除了while，还有until、recurse等$ echo 1|jq 'while(.<100; .*2)'1248163264# 自定义计算3次方的函数$ echo 2|jq 'def cube: .*.*. ; cube'8

由于这些高级特性并不常用，这里仅给出了一些简单示例，详细使用可以man jq查看。

辅助shell编程

熟悉shell脚本编程的同学都知道，shell本身是没有提供Map、List这种数据结构的，这导致使用shell实现某些功能时，变得很棘手。

但jq本身是处理json的，而json中的对象就可等同于Map，json中的数组就可等同于List，如下：

list='[]';#List添加元素list=$(echo "$list"|jq '. + [ $val ]' --arg val java);list=$(echo "$list"|jq '. + [ $val ]' --arg val shell);#获取List大小echo "$list"|jq '.|length'#获取List第1个元素echo "$list"|jq '.[0]' -r# List是否包含java字符串echo "$list"|jq 'any(.=="java")'#删除List第1个元素list=$(echo "$list"|jq 'del(.[0])');# List合并list=$(echo "$list"|jq '. + $val' --argjson val '["shell","python"]');# List截取echo "$list"|jq '.[1:3]'# List遍历for o in $(echo "$list" | jq -r '.[]');do     echo "$o"; donemap='{}';#Map添加元素map=$(echo "$map"|jq '.id=$val' --argjson val 1)map=$(echo "$map"|jq '.courses=$val' --argjson val "$list")#获取Map大小echo "$map"|jq '.|length'#获取Map指定key的值echo "$map"|jq '.id' -r#判断Map指定key是否存在echo "$map" | jq 'has("id")'#删除Map指定keymap=$(echo "$map"|jq 'del(.id)')# Map合并map=$(echo "$map"|jq '. + $val' --argjson val '{"code":"ID001","name":"hello"}')# Map的KeySet遍历for key in $(echo "$map" | jq -r 'keys[]'); do     value=$(jq '.[$a]' --arg a "$key" -r <<<"$map");     printf "%s:%s\n" "$key" "$value"; done# Map的entrySet遍历while read -r line; do     key=$(jq '.key' -r <<<"$line");     value=$(jq '.value' -r <<<"$line");     printf "%s:%s\n" "$key" "$value"; done <<<$(echo "$map" | jq 'to_entries[]' -c)

可以发现，jq已经实现了json数据处理与分析的方方面面，我个人最近在工作中，也多次使用jq来分析调用日志等，用起来确实非常方便。

如果你现在还没完全学会jq的用法，没关系，建议先收藏起来，后面一定会用得到的！