Issues using the tilde ~ in a simple function wrapper around scp

问题

I want place a simple bash function in my .bashrc that wraps around the scp command by accepting a 'source' argument and 'destination' argument, and so far have tried both

function send() {
eval "scp $1 user@annoyingly-long-server-name:$2"
}

and

function send() {
scp $1 user@annoyingly-long-server-name:$2
}

...but when I call either of the above a la

send file.txt ~/

I get the error scp: home-directory-on-remote-machine: Operation not supported. After echoing each argument, it seems that the tilde is expanded into the remote machine's home directory before evaluation. How can I prevent this?

回答1:

First of all, you can use ssh-keys to prevent typing of passwords.

Before you use your function do just once:

ssh-copy-id remoteHostName

It is considered better to use keys instead of passwords for ssh and that is true for scp.

Second, you don't need eval.

function send() {
    scp "$1" user@annoyingly-long-server-name:"$2"
}

And finally, you need to use explicit path names:

send foo /home/luke/foo

Because ~ is some how not properly evaluated to /home/luke/.

update, side story:

If your motivation for writing the function send is really that annoyingly-long-server-name you should know about /home/luke/.ssh/config. Inside this file you can do wonders:

Host a-nicer-alias
    Hostname stupid-host-name.verylongdoamin.com
    User luke

Then you can simply do scp a-nicer-alias

回答2:

I figured out a way to convert back from the expanded tilde to the string ~ inside the function using this thread. The function is now

function send() {
dest="$2"
dest="${dest/#$HOME/\~}"
scp $1 user@annoyingly-long-server-name:$dest
}

In the second line, if the string "$HOME" appears at the start of the second argument, it is replaced by a tilde ~. If the source and destination have identical $HOMEs and the user actually did supply the destination path explicitly, it won't do any harm to convert to ~, but if they do not have identical $HOMEs, it fixes the problem.

For some reason it seemed that I had to assign $2 to a variable before performing the string replacement.

来源：https://stackoverflow.com/questions/45317559/issues-using-the-tilde-in-a-simple-function-wrapper-around-scp

标签

Linux

bash

shell

scripting