Shell script to download file from UNIX system directory

Question

Can any one help me writing a shell script to Download files from Linux/UNIX system?

Regards

Answer 1

On UNIX systems, such as Linux and OSX, you have access to a utility called rsync. It is installed by default and is the tool to use to download files from another UNIX system.

It is a drop-in replacement for the cp (copy) command, but it is much more powerful.

To copy a directory from a remote system to yours, using SSH, you would do this:

rsync username@hostname:path/to/dir .

(notice the dot at the end, this means 'place everything here please', you can also give the name of the local dir where the files should be placed.)

To download only some specific files, use this:

rsync 'username@hostname:path/to/dir/*.txt' .

(notice the quotes: if you omit them, your shell will try to expand the *.txt part locally, will fail and give you an error.)

Useful flags:

--progress: show a progress bar
--append: if a file has only partially downloaded, resume it where it left off

I find the rsync utility so useful, I've created an alias for it in my shell and use it as a 'super-copy':

alias cpa 'rsync -vae ssh --progress --append'

With that alias, copying files between machines is just as easy as copying files locally:

cpa user@host:file .

Making it even better

Since rsync is using SSH, it helps to setup a private/public key pair, so you don't have to type in your password every time: How do I setup Public-Key Authentication?

Futhermore, you can write down your username in your .ssh/config file and give the remote host a short name: read about it here.

For example, I have something like this:

Host panda
    Hostname panda.server.long.hostname.com
    User rodin

With this setup, my command to download files from the panda server is just:

cpa panda:path/to/my/files .

And there was much rejoicing.