代码之家 › 专栏 › 技术社区 › damjandd

在shell脚本中使用jq迭代JSON对象

jq shell json

damjandd · 技术社区 · 8 年前

JSON结构如下所示:

{
   "items":[
      {
         "playlists":[
            {
               "title":"Level One Title",
               "courses":[
                  {
                     "title":"Level One Course One Title",
                     "lessons":[
                        {
                           "title":"lesson 1 title",
                           "url":"lesson 1 url"
                        },
                        {
                           "title":"lesson 2 title",
                           "url":"lesson 2 url"
                        }
                     ]
                  },
                  {
                     "title":"Level One Course Two Title",
                     "lessons":[
                        {
                           "title":"lesson 1 title",
                           "url":"lesson 1 url"
                        },
                        {
                           "title":"lesson 2 title",
                           "url":"lesson 2 url"
                        }
                     ]
                  }
               ]
            },
            {
               "title":"Level Two Title",
               "courses":[
                  {
                     "title":"Level Two Course One Title",
                     "lessons":[
                        {
                           "title":"lesson 1 title",
                           "url":"lesson 1 url"
                        },
                        {
                           "title":"lesson 2 title",
                           "url":"lesson 2 url"
                        }
                     ]
                  },
                  {
                     "title":"Level Two Course Two Title",
                     "lessons":[
                        {
                           "title":"lesson 1 title",
                           "url":"lesson 1 url"
                        },
                        {
                           "title":"lesson 2 title",
                           "url":"lesson 2 url"
                        }
                     ]
                  }
               ]
            }
         ]
      }
   ]
}

由于我是一名iOS开发者,我已经编写了一段模拟的Swift代码,可以实现我想要的。看起来是这样的:

for level in levels {
    let title = level["title"]
    //TODO: create a folder with title and set as pwd
    for course in level["courses"] {
        let courseTitle = course["title"]
        //TODO: create a folder with title and set as pwd
        for lesson in course["lessons"] {
            let title = lesson["title"]
            let videoURL = lesson["url"]
            //TODO: download video in current folder with title
        }
    }
}

levels Array 属于 Dictionaries , level 是其中之一 .每个级别包含一个属于 courses Dictionary ,包含 大堆 lesson 字典。

levels=$(jq ".items[0].playlists" data.json)
for level in $levels
do
    title=$($level | jq ".title")
    echo $title
done

这似乎根本不起作用。我想我在这里使用循环的逻辑是完全错误的。你知道怎么做吗?

1 回复 | 直到 8 年前

Charles Duffy 8 年前

将标题和URL提取到不同shell变量中的代码可能如下所示:

jq_program='
.items[].playlists[]            # we only care about playlist contents
| .title as $level_title        # store the level title before recursing
| .courses[]                    # ...into elements of the array in .courses...
| .title as $course_title       # repeat to store the course title
| .lessons[]                    # ...before recursing into the lesson...
# ...and emitting the stored level and course titles, plus the lesson title and url
| [$level_title, $course_title, .title, .url] | @tsv                              
'

while IFS=$'\t' read -r level_title course_title lesson_title lesson_url <&3; do
  mkdir -p -- "$level_title/$course_title"
  ## For test purposes, just store the URL in the file
  printf '%s\n' "$lesson_url" >"$level_title/$course_title/$lesson_title"
  ## If we had real data, we might instead be running something like:
  # curl -o "$level_title/$course_title/$lesson_title" "$lesson_url"
done 3< <(jq -r "$jq_program" <input.json)

这里,我们有 jq jq公司 ,但需要中讨论的解决方法之一 stedolan/jq#1271

BashFAQ #1 讨论我们在这里使用的技术,从 jq公司