理解CentOS7.4/docker terminal 编码 locale中文支持

• 获取编码格式

  From How to get terminal’s Character Encoding, the terminal uses environment variables to determine which character set to use, therefore you can determine it by looking at those variables: echo $LANG

• locale

  Locales are used in Linux to define which language and character set (encoding) user see in the terminal.

  Locale is defined in the following format:

  _.[@]

  ITEMs	FORMAT
  LANGUAGE	ISO 639 language code
  TERRITORY	ISO 3166 country code
  CODESET	Character set or encoding identifier, like ISO-8859-1 or UTF-8

  locale是一个综合性的概念，是根据计算机用户所使用的语言、所在国家或者地区、当地的文化传统所定义的一个软件运行时的语言环境。

  这个语言环境可以按照所涉及的不同领域划分成几大类：用户所使用的语言符号及其分类(LC_CTYPE)，数字 (LC_NUMERIC)，比较和排序习惯(LC_COLLATE)，时间显示格式(LC_TIME)，货币单位(LC_MONETARY)，信息主要是提示信息,错误信息, 状态信息, 标题, 标签, 按钮和菜单等(LC_MESSAGES)，姓名书写方式(LC_NAME)，地址书写方式(LC_ADDRESS)，电话号码书写方式 (LC_TELEPHONE)，度量衡表达方式(LC_MEASUREMENT)，默认纸张尺寸大小(LC_PAPER)和locale对自身包含信息的概述(LC_IDENTIFICATION)。

  这些locale定义文件放在/usr/share/i18n/locales目录下

• locale issues

  There are two questions: how to check and change the current locale and language settings from the command line in Linux.

  • check current locale and language settings

    # current locale and language settings
    $ locale 
    # list all enabled locales
    $ locale -a
    # list available encoding
    $ locale -m
    # locale and language settings are defined in the LANG variable
    $ echo $LANG
    

  • change the current locale and language settings

    • add new locale

      Before a locale can be enabled on the system, it must be generated.

      If you didn’t find the desired language or encoding in the list of enabled locales(locale -a), you can search for them in the list of all supported locales and install whatever you need.

      # for centos
      $ localedef --list-archive # list the all supported(available for generation) locales
      $ localedef -- list-archive | grep zh_CN.UTF-8 # find the desired locale 这一句好像无效
      $ sudo localedef -c -i zh_CN(locale定义文件) -f UTF-8(字符集) zh_CN.UTF-8 # generate it 
      $ locale -a | grep zh_CN.utf8 # available
      

    • already have useable locale

      To set the required locale and language for the current sesion - it is just needed to redefine LANG variable.

      $ LANG=zh_CN.utf8 # =两边不能有空格
      

      此方法设置后，echo $LANG 虽然显示zh_CN.utf8，但实际运行过程中中文还是乱码，而且locale命令下LANG未改变。

      $ export 
      

  • Define locale and language permanently

    Set the required value of the LANG variable in a user’s bash profile and the needed locale and language settings will be automatically loaded upon the each session.

    Put export LANG=zh_CN.utf8 line to the ~./bashrc or ~/.profile files.

    then source ~/.profile

• Dockerfile

  修改基础镜像中文locale支持

  RUN yum -y update \
      && yum install kde-l10n-Chinese -y \
      && yum reinstall glibc-common -y \
      && localedef -c -f UTF-8 -i zh_CN zh_CN.UTF-8 \
      && echo 'LANG="zh_CN.UTF-8"' > /etc/locale.conf \
      && source /etc/locale.conf
  ENV LC_ALL=zh_CN.UTF-8 \
      LANG=zh_CN.UTF-8
  

• Reference

1. Linux: Define Locale and Language Settings

2. 关于locale的设定,为什么要设定locale

3. CentOS7及Docker配置中文字符集问题