source command
命令的格式有两种
source .bashrc
. .bashrc
下面的方式更简洁，但后续的脚本如果要解析可能就稍微要复杂些。对应的文档：
. filename [arguments]
source filename [arguments]
Read and execute commands from filename in the current shell environment and return the exit status of the last command exe-
cuted from filename. If filename does not contain a slash, file names in PATH are used to find the directory containing file-
name. The file searched for in PATH need not be executable. When bash is not in posix mode, the current directory is searched
if no file is found in PATH. If the sourcepath option to the shopt builtin command is turned off, the PATH is not searched.
If any arguments are supplied, they become the positional parameters when filename is executed. Otherwise the positional
parameters are unchanged. The return status is the status of the last command exited within the script (0 if no commands are
executed), and false if filename is not found or cannot be read.
