Ansibleで設定ファイルの行を書き換える ref: http://qiita.com/komeda-shinji/items/fafc46e27e0619cade14

file0.txt

- hosts: servers
  vars:
    httpd_conf: /etc/apache2/apache2.conf
  tasks:
    - name: grep %{Session}C
      command: grep '^LogFormat[[:space:]].*%{Session}C.*[[:space:]]combined' {{httpd_conf}}
      register: grep
      ignore_errors: True
      failed_when: False
      changed_when: False
    - name: change httpd.conf
      lineinfile:
        backup=yes
        backrefs=yes
        dest={{httpd_conf}}
        state=present
        regexp="^(LogFormat\s+\")(.*)(\"\s+combined)$"
        line="\1\2 \\\\\"%{Session}C\\\\\" \3"
      when: grep.rc == 1