将 rlogin 命令转换为别名

Question

I work on multiple machines and need to login into them remotely. I want to have an alias which can make my rlogin command simpler.

So, I want to convert following command into an alias :

rlogin `echo "machine $num" | tr -d ' '`

I tried writing this in my .cshrc file :

alias rl rlogin `echo machine$1| tr -d ' '`

when I do rl 13

It says :

usage: rlogin [ -8EL] [-e char] [ -l username ] host

What am I missing here ?

Answer 1

You can easily see the alias is not defined as intended, by running alias rl :

% alias rl rlogin `echo machine$1| tr -d ' '`
% alias rl
rlogin machine

There are two problems with the way you define your alias.

First, when defining an alias like this:

alias rl rlogin `...`

the ... command is evaluated at the time the alias is defined , while you need to defer the evaluation to the time it is used. The correct way to do it is to encapsulate everything in single quotes, like

'`...`'

(Also, we need to replace the internal single-quotes with double-quotes, in order not to clash with the outer single-quotes).

Second, you need to use \\!* instead of $1 .

So you get:

% alias rl rlogin '`echo machine\!* | tr -d " "`'
% alias rl
rlogin `echo machine!* | tr -d " "`

Answer 2

The tr pipeline in your alias is useless. Simply saying:

alias rl 'rlogin machine\!:1'

and invoking it by saying:

rl 42

should work, ie should issue rlogin machine42 .

Note that you need to escape the ! in order to prevent it from being interpreted by the shell for history expansion.