command|command alias and source commandaliasandsource

alias make alias for commands.
alias display all alias
alias lb='ll -h'
make the change permanent:

append alias to ~/.bashrc
. ~/.bashrc or source ~/.bashrc

source source is a bash builtin command, which executes commands in the file.
file1:
echo hello
source file1
display:
hello
. is a shortcut for source, which means . file1 is same as source file1.
【command|command alias and source】Note that ./file1 will be executed in a new shell, while . file1 in the current shell.