The Magic DIrk

FreeBSD 默认的 shell 是 /bin/csh，相对于 Linux 下广泛使用的 /usr/ports/shell/bash 来说，默认设置的 /bin/csh 使用起来不太友好。比如命令补全功能，需要这样的设置。 /bin/csh 的历史命令功能是非常强大的：

For example, consider this bit of someone's history list:

     9  8:30    nroff -man wumpus.man
    10  8:31    cp wumpus.man wumpus.man.old
    11  8:36    vi wumpus.man
    12  8:37    diff wumpus.man.old wumpus.man

The commands are shown with their event numbers and time  stamps.   The
current  event,  which we haven't typed in yet, is event 13.  `!11' and
`!-2' refer to event 11.  `!!' refers to the previous event, 12.   `!!'
can  be  abbreviated  `!'  if  it  is followed by `:' (`:' is described
below).  `!n' refers to event 9, which begins with `n'.  `!?old?'  also
refers  to event 12, which contains `old'.  Without word designators or
modifiers history references simply expand to the entire event,  so  we
might  type  `!cp'  to redo the copy command or `!!|more' if the `diff'
output scrolled off the top of the screen.

默认的 /bin/csh 只保存 100 条历史命令，并且当你使用同一个账号开启多个连接到同一台服务器的时候，最终保存的历史命令可能只有最后退出那次会话的命令，其他连接中使用的命令没有保存起来。通过设置以下参数可以让 /bin/csh 合并多连接状态的历史命令：

set history = 2000
set savehist = 2000 merge

可以将以上设置保存到 /etc/csh.cshrc 或者 ~/.cshrc。（更多信息请参考“man csh”）