深入探索Shell配置与环境变量

# 深入探索Shell配置与环境变量 ## 1. 全局与本地配置文件 ### 1.1 全局配置文件 /etc/bashrc `/etc/bashrc` 的作用是设置系统范围的函数和别名，包括终端模拟器类型、命令提示符字符串、umask（定义新文件创建时的默认权限）以及 `$SHELL` 变量（定义bash shell可执行文件的全限定路径和名称）。 需要注意的是，用于bash shell全局配置的默认文件不应被修改。若要修改或添加全局配置，应在 `/etc/profile.d` 目录中添加自定义文件，文件名以 `.sh` 结尾即可，建议取一个容易识别的名字。 ### 1.2 本地配置文件 本地bash配置文件位于每个用户的主目录下，用户可修改这些文件以根据自己的偏好配置shell环境。主要的本地配置文件有 `.bashrc` 和 `.bash_profile`，它们包含一些基本的配置项。 当启动登录shell时，bash首先运行 `/etc/profile`，完成后运行 `~/.bash_profile`。以下是 `~/.bash_profile` 和 `~/.bashrc` 的内容示例： ```bash # ~/.bash_profile # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment and startup programs PATH=$PATH:$HOME/.local/bin:$HOME/bin export PATH ``` ```bash # ~/.bashrc # Source global definitions if [ -f /etc/bashrc ]; then . /etc/bashrc fi # Uncomment the following line if you don't like systemctl's auto-paging feature: # export SYSTEMD_PAGER= # User specific aliases and functions ``` `~/.bash_profile` 先运行 `~/.bashrc` 以设置别名和函数，然后设置并导出路径，使该路径对所有后续的非登录shell可用。`~/.bashrc` 会调用 `/etc/bashrc`。 ### 1.3 配置文件执行顺序 登录shell启动时的执行顺序如下： ```mermaid graph LR A[/etc/profile] --> B[~/.bash_profile] B --> C[~/.bashrc] C --> D[/etc/bashrc] ``` ## 2. 追踪配置脚本执行顺序 为了测试复杂且相互关联的shell程序或shell程序内过程的执行顺序，可以在每个相关程序的开头添加 `echo` 语句，以显示正在运行的shell程序。 ### 2.1 修改配置文件 以下是需要修改的文件及具体操作： - **/etc/profile**：在 `pathmunge` 过程之后添加 `echo "Running /etc/profile"`。 ```bash # /etc/profile # System wide environment and startup programs, for login setup # Functions and aliases go in /etc/bashrc # It's NOT a good idea to change this file unless you know what you # are doing. It's much better to create a custom.sh shell script in # /etc/profile.d/ to make custom changes to your environment, as this # will prevent the need for merging in future updates. pathmunge () { case ":${PATH}:" in *:"$1":*) ;; *) if [ "$2" = "after" ] ; then PATH=$PATH:$1 else PATH=$1:$PATH fi esac } echo "Running /etc/profile" if [ -x /usr/bin/id ]; then if [ -z "$EUID" ]; then # ksh workaround EUID=`id -u` UID=`id -ru` fi USER="`id -un`" LOGNAME=$USER MAIL="/var/spool/mail/$USER" fi ``` - **/etc/bashrc**：在文件开头添加 `echo "Running /etc/bashrc"`。 ```bash # /etc/bashrc # System wide functions and aliases # Environment stuff goes in /etc/profile # It's NOT a good idea to change this file unless you know what you # are doing. It's much better to create a custom.sh shell script in # /etc/profile.d/ to make custom changes to your environment, as this # will prevent the need for merging in future updates. echo "Running /etc/bashrc" # Prevent doublesourcing if [ -z ".bashrcSOURCED" ]; then .bashrcSOURCED="Y" ``` - **/etc/profile.d/myBashConfig.sh**：创建该文件并添加 `echo "Running /etc/profile.d/myBashConfig.sh"`。 ```bash # /etc/profile.d/myBashConfig.sh echo "Running /etc/profile.d/myBashConfig.sh" ``` - **~/.bash_profile**：在文件开头添加 `echo "Running ~/.bash_profile"`。 ```bash # .bash_profile echo "Running ~/.bash_profile" # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment and startup programs PATH=$PATH:$HOME/.local/bin:$HOME/bin export PATH ``` - **~/.bashrc**：在文件开头添加 `echo "Running ~/.bashrc"`。 ```bash # .bashrc echo ```