Automating ftp logins with netrc

If you are a regular ftp user, then netrc file can help you a lot in automating your logins and a few tasks you do via ftp.

Let us first consider automating ftp logins.

Create a ".netrc" file in your home directory. The access to this file should be restricted exclusively to you.

cd ~;touch .netrc;chmod u+rw,go= .netrc

Now assume you need to connect to an ftp server "myftp.safeer.in" with username 'safeer' and password 'password#123'. To automate this, add the following line to your .netrc file.

machine myftp.safeer.in login safeer password password#123

Here machine defines the host you want to login to, login is your username for the host and password is the password for this username.

safeer@my-lptp01:~$ ftp myftp.safeer.in
Connected to myftp.safeer.in.
220 (vsFTPd 2.0.7)
331 Please specify the password.
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>

You can define a line for each of the host you want to login. If you use the same login for many of the ftp hosts, you can use the default entry like this.

default login safeer password password#123

With this entry, if you connect to an ftp host which is not explicitly defined in netrc with a "machine" entry, the login and password from the default line will be used. If you want to disable the autologin feature of netrc while running ftp program, use the option "-n", ie; "ftp -n [ftphost]"

safeer@my-lptp01:~$ ftp -n myftp.safeer.in
Connected to myftp.safeer.in.
220 (vsFTPd 2.0.7)
ftp> pwd
530 Please login with USER and PASS.

Thats all about auto logins, now let us see how to automate tasks. We use ftp "macros" for this. FTP macros are nothing but an ordered set of ftp commands grouped with a macro name, similar to a bash function/script. You can use the macro name like another command and execute the commands included with it.

Creating a macro with name "fmacro"

macdef fmacro
cd /home/safeer/pub/site_backup
put webdata.tar.gz

Now, run the macro:

ftp> $fmacro
cd /home/safeer/pub/site_backup
250 Directory successfully changed.
put webdata.tar.gz
local: webdata.tar.gz remote: webdata.tar.gz
200 PORT command successful. Consider using PASV.
150 Ok to send data.
226 File receive OK.
ftp>

A macro defined by the name "init" (in netrc file) will be run every time you login to the corresponding ftp host. Each macro definition is associated with the login entry preceding it and terminated by a blank line. You can't define global macros in netrc file. Macros associated with the" default" entry will work for all machines that are not explicitly defined in the file. To know more about ftp macros, visit this link.

For each "machine" line you can use one or more of the variables machine,login,password in order. ie: any of the following will work.

machine myftp.safeer.in login safeer password password#123 OR
machine myftp.safeer.in login safeer OR
machine myftp.safeer.in

The last option will be used only if you want to define some macros for this host, but don't want the autologin feature. While defining the default entry, make sure that it is defined as the last entry in the file. This is necessary as netrc is processed sequentially and accepts the first entry that matches the connecting host. For more information on netrc and macros, see man pages for netrc and ftp.