When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. The --noprofile option may be used when the shell is started to inhibit this behavior.
When a login shell exits, bash reads and executes commands from the files ~/.bash_logout and /etc/bash.bash_logout, if the files exists.
When an interactive shell that is not a login shell is started, bash reads and executes commands from ~/.bashrc, if that file exists. This may be inhibited by using the –norc option. The –rcfile file option will force bash to read and execute commands from file instead of ~/.bashrc.
[root@localhost ~]# head /etc/profile # /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.
[root@localhost ~]# head /etc/bashrc # /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.
An interactive shell is one started without non-option arguments and without the -c option whose standard input and error are both connected to terminals (as determined by isatty(3)), or one started with the -i option.
这个目录对于系统来说也是一个非常重要的目录,其地位类似 Windows 上面的”Program Files”目录。安装程序的时候,默认就是安装在此文件内部某个子文件夹内。输入命令后系统默认执行 /usr/bin 下的程序(当然,前提是这个目录的路径已经被添加到了系统的环境变量中)。此目录通常也会挂载一个独立的磁盘分区,它应保存共享只读类文件,这样它可以被运行 Linux 的不同主机挂载。