在 YAML 中，可以通过两种方式将字符串分行显示：使用“|”（Literal Block Scalar）和“>”（Folded Block Scalar）操作符。这两种方式在处理多行文本时的行为有所不同。

1. “|” - Literal Block Scalar

使用“|”操作符时，YAML 会保留字符串中的换行符和空格，将多行文本原样输出。

示例代码：

variable1: |
  exactly as you see
  will appear these three
  lines of poetry

输出结果：

variable1: "exactly as you see\nwill appear these three\nlines of poetry\n"

2. “>” - Folded Block Scalar

使用“>”操作符时，YAML 会将多行文本折叠成单行，将换行符替换为空格。

示例代码：

variable2: >
  this is really a
  single line of text
  despite appearances

输出结果：

variable2: "this is really a single line of text despite appearances\n"

如何去除字符串末尾的换行符

如果不想在字符串末尾保留换行符，可以在操作符后添加“-”（减号）。

示例代码：

variable1: |-
  exactly as you see
  will appear these three
  lines of poetry

variable2: >-
  this is really a
  single line of text
  despite appearances

输出结果：

variable1: "exactly as you see\nwill appear these three\nlines of poetry"
variable2: "this is really a single line of text despite appearances"

示例：在 Ansible Playbook 中使用多行字符串

示例代码

---
- name: debug module demo
  hosts: all
  vars:
    variable1: |
      exactly as you see
      will appear these three
      lines of poetry
    variable2: >
      this is really a
      single line of text
      despite appearances
  tasks:
    - name: print variable1
      ansible.builtin.debug:
        var: variable1

    - name: print variable2
      ansible.builtin.debug:
        var: variable2

执行结果

$ ansible-playbook -i virtualmachines/demo/inventory print\ text\ variable\ during\ execution/multi-line.yml
PLAY [debug module demo] **********************************
TASK [Gathering Facts] ************************************
ok: [demo.example.com]
TASK [print variable1] ************************************
ok: [demo.example.com] => {
    "variable1": "exactly as you see\nwill appear these three\nlines of poetry\n"
}
TASK [print variable2] ************************************
ok: [demo.example.com] => {
    "variable2": "this is really a single line of text despite appearances\n"
}
PLAY RECAP *************************************************
demo.example.com           : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

示例：去除字符串末尾的换行符

示例代码

---
- name: debug module demo
  hosts: all
  vars:
    variable1: |-
      exactly as you see
      will appear these three
      lines of poetry
    variable2: >-
      this is really a
      single line of text
      despite appearances
  tasks:
    - name: print variable1
      ansible.builtin.debug:
        var: variable1

    - name: print variable2
      ansible.builtin.debug:
        var: variable2

执行结果

$ ansible-playbook -i virtualmachines/demo/inventory print\ text\ variable\ during\ execution/multi-line.yml
PLAY [debug module demo] **********************************
TASK [Gathering Facts] ************************************
ok: [demo.example.com]
TASK [print variable1] ************************************
ok: [demo.example.com] => {
    "variable1": "exactly as you see\nwill appear these three\nlines of poetry"
}
TASK [print variable2] ************************************
ok: [demo.example.com] => {
    "variable2": "this is really a single line of text despite appearances"
}
PLAY RECAP *************************************************
demo.example.com           : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

示例：将多行字符串拆分为列表

示例代码

---
- name: debug module demo
  hosts: all
  vars:
    variable1: |-
      exactly as you see
      will appear these three
      lines of poetry
    variable2: >-
      this is really a
      single line of text
      despite appearances
  tasks:
    - name: print variable1
      ansible.builtin.debug:
        msg: "{{ variable1.split('\n') }}"

    - name: print variable2
      ansible.builtin.debug:
        var: variable2

执行结果

$ ansible-playbook -i virtualmachines/demo/inventory print\ text\ variable\ during\ execution/multi-line.yml
PLAY [debug module demo] **********************************
TASK [Gathering Facts] ************************************
ok: [demo.example.com]
TASK [print variable1] ************************************
ok: [demo.example.com] => {
    "msg": [
        "exactly as you see",
        "will appear these three",
        "lines of poetry"
    ]
}
TASK [print variable2] ************************************
ok: [demo.example.com] => {
    "variable2": "this is really a single line of text despite appearances"
}
PLAY RECAP *************************************************
demo.example.com           : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

总结

  • 使用“|”操作符时，多行文本将保留换行符和空格，原样输出。
  • 使用“>”操作符时，多行文本将折叠成单行，换行符被替换为空格。
  • 如果不想保留末尾的换行符，可以在操作符后添加“-”。
  • 可以通过 .split('\n') 方法将多行字符串拆分为列表，方便进一步处理。