What is the source command in Linux?

Http://zhidao.baidu.com/question/378390415.html

 

Command usage: Source filename function: read and execute the command in filename in the current bash environment. Note: This command is usually replaced by the "." command. For example, source/etc/profile is equivalent to./etc/profile. Note: The difference between the source command and shell scripts is that the source command is executed in the current bash environment, and the scripts is to start a sub-shell to execute the command. In this way, if you write the commands for setting environment variables (or alias) into scripts, it will only affect the sub-shell and cannot change the current bash. Therefore, through the file (command column) when setting environment variables, use the source command.