刪除別名

要刪除現有別名，請使用：

 placeholderCopyunalias {alias_name}

例：

 placeholderCopy# create an alias    
$ alias now='date'

# preview the alias
$ now
Thu Jul 21 17:11:25 CEST 2016

# remove the alias
$ unalias now

# test if removed
$ now
-bash: now: command not found