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### 5.13 Remote Files

GPS has a basic support for working with files on remote hosts. This includes a number of protocols, described below, which allow you to read a file from a remote host, edit it locally, and then save it transparently to the remote machine.

For now, the support for remote files is only available through the GPS shell window. You start editing a remote file by typing a line similar to

         Editor.edit protocol://user@machine/full/path

where "protocol" should be replaced by the name of the protocol you want to use, "user" is the login name you wish to use on the remote "machine", and "/full/path" is the full path on the remote machine to access the file.

The user name is optional. If it is the same as on the local machine, you can omit the user name as well as the "@" sign.

Likewise, the machine name is optional, if you want to get a file from the local host. This can be used to access files belonging to another user. In this case, you need to specify the "@" sign, but do not insert a machine name right after it.

Remote files can also be used if you want to work with GPS, but the machine on which the files are found isn't supported by GPS.

The following protocols are supported:

ssh
  This protocol is based on the ssh command line tool, which must therefore be available in the path. It provides encrypted and secure connections to the remote host. Files are transfered in-line, that is the connection is established the first time you access the remote host, and kept open for all further access.

  Although ssh can be setup not to require a password, GPS will automatically detect if a password is asked and open a dialog to query it.

  The remote system must be a Unix-like system with support for standard Unix commands like `test`, `echo`, `rm` and `ls`.

  In the sample shell command above, you would replace the word "protocol" with "ssh" to use this protocol.

rsh
  This protocol behaves like ssh, except that the connections are not encrypted. However, this protocol is generally available on all Unix machines by default.

  It has the same requirements that the ssh protocol. To use it, substitute the word "rsh" to "protocol" in the example above.

telnet
  This protocol is based on the standard telnet protocol. It behaves much like the two protocols above, with an unencrypted connection.

  To use it, substitute the word "telnet" to "protocol" in the example above.

scp
  This protocol is also based on one of the tools of the ssh suite. It provides encrypted connections, and uses a mixture of ssh and scp connections. Various commands like querying the time stamp of a file are executed through a permanent ssh connection, whereas files are downloaded and uploaded through a one-time scp command.

  It basically has the same behavior as the ssh protocol, although it might be slightly slower since a new connection has to be established every time a file is fetched from, or written to the remote host. However, it might work better than ssh if the file contains 8 bit characters.

  To use it, substitute the word "scp" to "protocol" in the example above.

rsync
  Just like scp is based on ssh, this protocol is based on either rsh or ssh. It depends on the external tool rsync, and uses a mixture of a rsh/ssh connection for commands like querying the time stamp of a file, and one-time connections with rsync to transfer the files.

  Rsync is specially optimized to transfer only the parts of a file that are different from the one already on the remote host. Therefore, it will generally provide the best performance when writing the file back to the remote host.

  If you set up the environment variable RSYNC_RSH to ssh before starting gps, the connection will then be encrypted when transferring the files, and the connection will be performed using ssh instead of rsh.

  To use this protocol, substitute the word "rsync" to "protocol" in the example above.

ftp
  This protocol provides only limited capabilities, but can be used to retrieve or write a file back through an ftp connection, possibly even through an anonymous ftp connection.

  To use this protocol, substitute the word "ftp" to "protocol" in the example above.

http
  This is the usual http protocol to download documents from the web. It is in particular useful for documentation