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

• 獲取編碼格式

  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:

  <LANGUAGE>_<TERRITORY>.<CODESET>[@<MODIFIERS>]

  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是一個綜合性的概念，是根據計算機用戶所使用的語言、所在國家或者地區、當地的文化傳統所定義的一個軟件運行時的語言環境。

  這個語言環境可以按照所涉及的不同領域劃分成幾大類：用戶所使用的語言符號及其分類(LC_CTYPE)，數字 (LC_NUMERIC)，比較和排序習慣(LC_COLLATE)，時間顯示格式(LC_TIME)，貨幣單位(LC_MONETARY)，信息主要是提示信息,錯誤信息, 狀態信息, 標題, 標籤, 按鈕和菜單等(LC_MESSAGES)，姓名書寫方式(LC_NAME)，地址書寫方式(LC_ADDRESS)，電話號碼書寫方式 (LC_TELEPHONE)，度量衡表達方式(LC_MEASUREMENT)，默認紙張尺寸大小(LC_PAPER)和locale對自身包含信息的概述(LC_IDENTIFICATION)。

  這些locale定義文件放在/usr/share/i18n/locales目錄下

• 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 這一句好像無效
      $ sudo localedef -c -i zh_CN(locale定義文件) -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 # =兩邊不能有空格
      

      此方法設置後，echo $LANG 雖然顯示zh_CN.utf8，但實際運行過程中中文還是亂碼，而且locale命令下LANG未改變。

      $ 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

  修改基礎鏡像中文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. 關於locale的設定,爲什麼要設定locale

3. CentOS7及Docker配置中文字符集問題