我知道我的回答很具体，但是如果已经安装了PHP和Symfony，那么使用Symfony的YAML解析器会非常方便。

例如:

php -r "require '$SYMFONY_ROOT_PATH/vendor/autoload.php'; \
    var_dump(\Symfony\Component\Yaml\Yaml::parse(file_get_contents('$YAML_FILE_PATH')));"

这里我只是简单地使用var_dump来输出解析后的数组，当然你还可以做更多…：）

很难说，因为这取决于您希望解析器从YAML文档中提取什么。对于简单的情况，你可以使用grep、cut、awk等。对于更复杂的解析，您需要使用成熟的解析库，如Python的PyYAML或YAML::Perl。

我曾经使用python将yaml转换为json，并在jq中进行处理。

python -c "import yaml; import json; from pathlib import Path; print(json.dumps(yaml.safe_load(Path('file.yml').read_text())))" | jq '.'

可以将一个小脚本传递给一些解释器，比如Python。使用Ruby和它的YAML库的简单方法如下:

$ RUBY_SCRIPT="data = YAML::load(STDIN.read); puts data['a']; puts data['b']"
$ echo -e '---\na: 1234\nb: 4321' | ruby -ryaml -e "$RUBY_SCRIPT"
1234
4321

，其中data是来自yaml的值的散列(或数组)。

作为奖励，它可以很好地解析杰基尔的正面问题。

ruby -ryaml -e "puts YAML::load(open(ARGV.first).read)['tags']" example.md

如果您知道您感兴趣的标记和您期望的yaml结构，那么在Bash中编写一个简单的yaml解析器并不难。

在下面的示例中，解析器将一个结构化YAML文件读入环境变量、数组和关联数组。

注意:这个解析器的复杂性与YAML文件的结构有关。对于YAML文件的每个结构化组件，都需要一个单独的子例程。高度结构化的YAML文件可能需要更复杂的方法，例如通用的递归下降解析器。

圣诞节。yaml文件:

# Xmas YAML example
---
 # Values
 pear-tree: partridge
 turtle-doves: 2.718
 french-hens: 3

 # Array
 calling-birds:
   - huey
   - dewey
   - louie
   - fred

 # Structure
 xmas-fifth-day:
   calling-birds: four
   french-hens: 3
   golden-rings: 5
   partridges:
     count: 1
     location: "a pear tree"
   turtle-doves: two

解析器使用mapfile将文件作为数组读入内存，然后循环遍历每个标记并创建环境变量。

梨树、斑鸠和法国母鸡:最终成为简单的环境变量 呼叫鸟:变成一个数组 xmas-fifth-day:结构被表示为一个关联数组，但是如果您没有使用Bash 4.0或更高版本，您可以将这些数组编码为环境变量。 注释和空白将被忽略。

#!/bin/bash
# -------------------------------------------------------------------
# A simple parser for the xmas.yaml file
# -------------------------------------------------------------------
# 
# xmas.yaml tags
#  #                        - Ignored
#                           - Blank lines are ignored
#  ---                      - Initialiser for days-of-xmas 
#   pear-tree: partridge    - a string
#   turtle-doves: 2.718     - a string, no float type in Bash
#   french-hens: 3          - a number
#   calling-birds:          - an array of strings
#     - huey                - calling-birds[0]
#     - dewey
#     - louie
#     - fred
#   xmas-fifth-day:         - an associative array
#     calling-birds: four   - a string
#     french-hens: 3        - a number
#     golden-rings: 5       - a number
#     partridges:           - changes the key to partridges.xxx
#       count: 1            - a number
#       location: "a pear tree" - a string
#     turtle-doves: two     - a string
# 
# This requires the following routines
# ParseXMAS
#   parses #, ---, blank line
#   unexpected tag error
#   calls days-of-xmas
#
# days-of-xmas
#   parses pear-tree, turtle-doves, french-hens
#   calls calling-birds
#   calls xmas-fifth-day
# 
# calling-birds
#   elements of the array
#
# xmas-fifth-day
#   parses calling-birds, french-hens, golden-rings, turtle-doves
#   calls partridges
# 
# partridges
#   parses partridges.count, partridges.location
#

function ParseXMAS()
{

  # days-of-xmas
  #   parses pear-tree, turtle-doves, french-hens
  #   calls calling-birds
  #   calls xmas-fifth-day
  # 
  function days-of-xmas()
  {
    unset PearTree TurtleDoves FrenchHens

    while [ $CURRENT_ROW -lt $ROWS ]
    do
      LINE=( ${CONFIG[${CURRENT_ROW}]} )
      TAG=${LINE[0]}
      unset LINE[0]

      VALUE="${LINE[*]}"

      echo "  days-of-xmas[${CURRENT_ROW}] ${TAG}=${VALUE}"

      if [ "$TAG" = "pear-tree:" ]
      then
        declare -g PearTree=$VALUE
      elif [ "$TAG" = "turtle-doves:" ]
      then
        declare -g TurtleDoves=$VALUE
      elif [ "$TAG" = "french-hens:" ]
      then
        declare -g FrenchHens=$VALUE
      elif [ "$TAG" = "calling-birds:" ]
      then
        let CURRENT_ROW=$(($CURRENT_ROW + 1))
        calling-birds
        continue
      elif [ "$TAG" = "xmas-fifth-day:" ]
      then
        let CURRENT_ROW=$(($CURRENT_ROW + 1))
        xmas-fifth-day
        continue
      elif [ -z "$TAG" ] || [ "$TAG" = "#" ]
      then
        # Ignore comments and blank lines
        true
      else
        # time to bug out
        break
      fi

      let CURRENT_ROW=$(($CURRENT_ROW + 1))
    done
  }

  # calling-birds
  #   elements of the array
  function calling-birds()
  {
    unset CallingBirds

    declare -ag CallingBirds

    while [ $CURRENT_ROW -lt $ROWS ]
    do
      LINE=( ${CONFIG[${CURRENT_ROW}]} )
      TAG=${LINE[0]}
      unset LINE[0]

      VALUE="${LINE[*]}"

      echo "    calling-birds[${CURRENT_ROW}] ${TAG}=${VALUE}"

      if [ "$TAG" = "-" ]
      then
        CallingBirds[${#CallingBirds[*]}]=$VALUE
      elif [ -z "$TAG" ] || [ "$TAG" = "#" ]
      then
        # Ignore comments and blank lines
        true
      else
        # time to bug out
        break
      fi

      let CURRENT_ROW=$(($CURRENT_ROW + 1))
    done
  }

  # xmas-fifth-day
  #   parses calling-birds, french-hens, golden-rings, turtle-doves
  #   calls fifth-day-partridges
  # 
  function xmas-fifth-day()
  {
    unset XmasFifthDay

    declare -Ag XmasFifthDay

    while [ $CURRENT_ROW -lt $ROWS ]
    do
      LINE=( ${CONFIG[${CURRENT_ROW}]} )
      TAG=${LINE[0]}
      unset LINE[0]

      VALUE="${LINE[*]}"

      echo "    xmas-fifth-day[${CURRENT_ROW}] ${TAG}=${VALUE}"

      if [ "$TAG" = "calling-birds:" ]
      then
        XmasFifthDay[CallingBirds]=$VALUE
      elif [ "$TAG" = "french-hens:" ]
      then
        XmasFifthDay[FrenchHens]=$VALUE
      elif [ "$TAG" = "golden-rings:" ]
      then
        XmasFifthDay[GOLDEN-RINGS]=$VALUE
      elif [ "$TAG" = "turtle-doves:" ]
      then
        XmasFifthDay[TurtleDoves]=$VALUE
      elif [ "$TAG" = "partridges:" ]
      then
        let CURRENT_ROW=$(($CURRENT_ROW + 1))
        partridges
        continue
      elif [ -z "$TAG" ] || [ "$TAG" = "#" ]
      then
        # Ignore comments and blank lines
        true
      else
        # time to bug out
        break
      fi
 
      let CURRENT_ROW=$(($CURRENT_ROW + 1))
    done
  }

  function partridges()
  {
    while [ $CURRENT_ROW -lt $ROWS ]
    do
      LINE=( ${CONFIG[${CURRENT_ROW}]} )
      TAG=${LINE[0]}
      unset LINE[0]

      VALUE="${LINE[*]}"

      echo "      partridges[${CURRENT_ROW}] ${TAG}=${VALUE}"

      if [ "$TAG" = "count:" ]
      then
        XmasFifthDay[PARTRIDGES.COUNT]=$VALUE
      elif [ "$TAG" = "location:" ]
      then
        XmasFifthDay[PARTRIDGES.LOCATION]=$VALUE
      elif [ -z "$TAG" ] || [ "$TAG" = "#" ]
      then
        # Ignore comments and blank lines
        true
      else
        # time to bug out
        break
      fi
 
      let CURRENT_ROW=$(($CURRENT_ROW + 1))
    done
  }

  # ===================================================================
  # Load the configuration file

  mapfile CONFIG < xmas.yaml

  let ROWS=${#CONFIG[@]}
  let CURRENT_ROW=0

  # +
  # #
  #
  # ---
  # -
  while [ $CURRENT_ROW -lt $ROWS ]
  do
    LINE=( ${CONFIG[${CURRENT_ROW}]} )
    TAG=${LINE[0]}
    unset LINE[0]

    VALUE="${LINE[*]}"

    echo "[${CURRENT_ROW}] ${TAG}=${VALUE}"

    if [ "$TAG" = "---" ]
    then
        let CURRENT_ROW=$(($CURRENT_ROW + 1))
        days-of-xmas
        continue
    elif [ -z "$TAG" ] || [ "$TAG" = "#" ]
    then
        # Ignore comments and blank lines
        true
    else
        echo "Unexpected tag at line $(($CURRENT_ROW + 1)): <${TAG}>={${VALUE}}"
        break
    fi

    let CURRENT_ROW=$(($CURRENT_ROW + 1))
  done
}

echo =========================================
ParseXMAS

echo =========================================
declare -p PearTree
declare -p TurtleDoves
declare -p FrenchHens
declare -p CallingBirds
declare -p XmasFifthDay

这将产生以下输出

=========================================
[0] #=Xmas YAML example
[1] ---=
  days-of-xmas[2] #=Values
  days-of-xmas[3] pear-tree:=partridge
  days-of-xmas[4] turtle-doves:=2.718
  days-of-xmas[5] french-hens:=3
  days-of-xmas[6] =
  days-of-xmas[7] #=Array
  days-of-xmas[8] calling-birds:=
    calling-birds[9] -=huey
    calling-birds[10] -=dewey
    calling-birds[11] -=louie
    calling-birds[12] -=fred
    calling-birds[13] =
    calling-birds[14] #=Structure
    calling-birds[15] xmas-fifth-day:=
  days-of-xmas[15] xmas-fifth-day:=
    xmas-fifth-day[16] calling-birds:=four
    xmas-fifth-day[17] french-hens:=3
    xmas-fifth-day[18] golden-rings:=5
    xmas-fifth-day[19] partridges:=
      partridges[20] count:=1
      partridges[21] location:="a pear tree"
      partridges[22] turtle-doves:=two
    xmas-fifth-day[22] turtle-doves:=two
=========================================
declare -- PearTree="partridge"
declare -- TurtleDoves="2.718"
declare -- FrenchHens="3"
declare -a CallingBirds=([0]="huey" [1]="dewey" [2]="louie" [3]="fred")
declare -A XmasFifthDay=([CallingBirds]="four" [PARTRIDGES.LOCATION]="\"a pear tree\"" [FrenchHens]="3" [GOLDEN-RINGS]="5" [PARTRIDGES.COUNT]="1" [TurtleDoves]="two" )

Whenever you need a solution for "How to work with YAML/JSON/compatible data from a shell script" which works on just about every OS with Python (*nix, OSX, Windows), consider yamlpath, which provides several command-line tools for reading, writing, searching, and merging YAML, EYAML, JSON, and compatible files. Since just about every OS either comes with Python pre-installed or it is trivial to install, this makes yamlpath highly portable. Even more interesting: this project defines an intuitive path language with very powerful, command-line-friendly syntax that enables accessing one or more nodes.

针对您的具体问题，在使用Python的本地包管理器或您的操作系统的包管理器安装yamlpath之后(yamlpath可以通过RPM对某些操作系统提供):

#!/bin/bash
# Read values directly from YAML (or EYAML, JSON, etc) for use in this shell script:
myShellVar=$(yaml-get --query=any.path.no[matter%how].complex source-file.yaml)

# Use the value any way you need:
echo "Retrieved ${myShellVar}"

# Perhaps change the value and write it back:
myShellVar="New Value"
yaml-set --change=/any/path/no[matter%how]/complex --value="$myShellVar" source-file.yaml

不过，您没有指定数据是一个简单的Scalar值，因此让我们提高赌注。如果你想要的结果是一个数组呢?更有挑战性的是，如果它是一个哈希数组，而你只想要每个结果的一个属性呢?进一步假设您的数据实际上分布在多个YAML文件中，并且您需要在单个查询中获得所有结果。这是一个更有趣的问题。所以，假设你有这两个YAML文件:

文件:data1.yaml

---
baubles:
  - name: Doohickey
    sku: 0-000-1
    price: 4.75
    weight: 2.7g
  - name: Doodad
    sku: 0-000-2
    price: 10.5
    weight: 5g
  - name: Oddball
    sku: 0-000-3
    price: 25.99
    weight: 25kg

文件:data2.yaml

---
baubles:
  - name: Fob
    sku: 0-000-4
    price: 0.99
    weight: 18mg
  - name: Doohickey
    price: 10.5
  - name: Oddball
    sku: 0-000-3
    description: This ball is odd

在应用数据2的更改后，如何仅报告库存中每个项目的sku。Yaml到data1。Yaml，所有从一个shell脚本?试试这个:

#!/bin/bash
baubleSKUs=($(yaml-merge --aoh=deep data1.yaml data2.yaml | yaml-get --query=/baubles/sku -))

for sku in "${baubleSKUs[@]}"; do
    echo "Found bauble SKU:  ${sku}"
done

你只需要几行代码就能得到你想要的东西:

Found bauble SKU:  0-000-1
Found bauble SKU:  0-000-2
Found bauble SKU:  0-000-3
Found bauble SKU:  0-000-4

如您所见，yamlpath将非常复杂的问题转化为简单的解决方案。注意，整个查询是作为一个流处理的;查询没有更改YAML文件，也没有临时文件。

I realize this is "yet another tool to solve the same question" but after reading the other answers here, yamlpath appears more portable and robust than most alternatives. It also fully understands YAML/JSON/compatible files and it does not need to convert YAML to JSON to perform requested operations. As such, comments within the original YAML file are preserved whenever you need to change data in the source YAML file. Like some alternatives, yamlpath is also portable across OSes. More importantly, yamlpath defines a query language that is extremely powerful, enabling very specialized/filtered data queries. It can even operate against results from disparate parts of the file in a single query.

If you want to get or set many values in the data at once -- including complex data like hashes/arrays/maps/lists -- yamlpath can do that. Want a value but don't know precisely where it is in the document? yamlpath can find it and give you the exact path(s). Need to merge multiple data file together, including from STDIN? yamlpath does that, too. Further, yamlpath fully comprehends YAML anchors and their aliases, always giving or changing exactly the data you expect whether it is a concrete or referenced value.

免责声明:我编写并维护了yamlpath，它是基于ruamel的。yaml是基于PyYAML的。因此，yamlpath完全符合标准。