jq 创建一个具有嵌套结构的数组

Question

我有一个包含多行的文件。 文件:

row1
row2

对于每一行，我想创建以下内容，其中第一组读取的后缀为“first”，第二组读取的后缀为“last”

[
  {
    "forward": "forward-row1-first",
    "reverse": "reverse-row1-first"
      },
  {
    "forward": "forward-row1-last",
    "reverse": "reverse-row1-last"
      }
]

接下来，我想将文件中每一行的上述结构组合起来，如下所示:

[
  {
    "reads": [
      {
        "forward": "forward-row1-first",
        "reverse": "reverse-row1-first"
      },
      {
        "forward": "forward-row1-last",
        "reverse": "reverse-row1-last"
      }
    ]
  },
  {
    "reads": [
      {
        "forward": "forward-row2-first",
        "reverse": "reverse-row2-first"
      },
      {
        "forward": "forward-row2-last",
        "reverse": "reverse-row2-last"
      }
    ]
  }
]

我有以下代码:

create_json () {
  ROW="$1"

  for SUFFIX in 1 2; do
    FORWARD="forward-${ROW}_${SUFFIX}"
    REVERSE="reverse-${ROW}_${SUFFIX}"
    jq -n --arg forward "$FORWARD" --arg reverse "$REVERSE" '{forward: $forward, reverse: $reverse}'
  done | jq -n '.reads |= [inputs]'
}

DATA=()

while read -r line; do
    DATA+=($(create_json $line))
done < prefixes.txt

echo "${DATA[*]}"

这种方法的问题在于，文件中每一行的 json 对象都附加到 bash 数组中，输出如下所示:

{ "reads": [ { "forward": "forward-row1_first", "reverse": "reverse-row1_first" }, { "forward": "forward-row1_last", "reverse": "reverse-row1_last" } ] } { "reads": [ { "forward": "forward-row2_first", "reverse": "reverse-row2_first" }, { "forward": "forward-row2_last", "reverse": "reverse-row2_last" } ] }

如何以优雅的方式使用 jq 来获得所需的输出格式？

Answer 1

您可以使用-R选项读取行文本文件。要迭代输入，还可以使用-n选项从第一行开始。

jq -Rn '
  reduce inputs as $row ([]; . += [{reads: [("first", "last") as $sfx | {
    forward: "forward-\($row)-\($sfx)",
    reverse: "reverse-\($row)-\($sfx)"
  }]}])
' rows.txt

[
  {
    "reads": [
      {
        "forward": "forward-row1-first",
        "reverse": "reverse-row1-first"
      },
      {
        "forward": "forward-row1-last",
        "reverse": "reverse-row1-last"
      }
    ]
  },
  {
    "reads": [
      {
        "forward": "forward-row2-first",
        "reverse": "reverse-row2-first"
      },
      {
        "forward": "forward-row2-last",
        "reverse": "reverse-row2-last"
      }
    ]
  }
]