Provide commands automatically to ftp in bash script

Question

I am trying to create a bash script with ftp.

If I use terminal and put the commands below one bye one, it works like a charm.

$ ftp 192.168.1.4 2121
Connected to 192.168.1.4.
220 SwiFTP 1.7.11 ready
Name (192.168.1.4:user): 
331 Send password
Password:
230 Access granted
Remote system type is UNIX.
Using binary mode to transfer files.

ftp> cd Study/Math
ftp> put ~/Documents/Math/lesson.pdf lesson.pdf

I am trying to automate this command with a bash script:

#!/bin/bash
ftp 192.168.1.4 2121
cd Study/Math
put ~/Documents/Math/lesson.pdf lesson.pdf

It is not working. I know here ftp is a independent tool and I have to put those command while the ftp program is running. I searched internet tried various techniques (like printf, expect, etc...) but it did not worked. I also tried to use some scripts from internet to automate this process, but nothing helped. I am a newbie in bash scripting and these stuffs. Can you guys help me to solve this Problem? Thanks in advance...

Answer 1

First, don't do this if you have any other option. It's a fairly standard idiom, but it's really broken in a lot of ways. If you're very sure that it won't ever do anything unpredictable, and that when it does it will be ok anyway, then sure, but in general...

1. use something besides ftp. For example, scp works quite well and has a checkable return code that is actually useful.

2. use a more granular programming language with modules. Don't get me wrong, I love bash and will always use it first when I can, but pumping a stream of commands into an ftp like a fire-and-forget UDP torpedo without any easy way of checking that each worked is just bad habit. Try Perl, or Python, or any other damned thing that lets you check a return code on each command and react accordingly. :)

3. if you MUST use bash (and yes, I have done it), and if it's important enough to check (what isn't?), then think about how you're going to do that. Maybe you can just pull lesson.pdf back to a local testme.pdf and cmp them to make sure it's good, which seems pretty easy. For any more complex script, you might need to run the ftp as a coprocesses and feed it commands one at a time, then read back it's output and parse for return codes, because ftp generally only reports errors there...and watch out for "500 bytes sent", which isn't a 500 error.

Either way, good luck. In many ways, simple is still best.

Answer 2

You might be interested in what is known as a heredoc

#!/usr/bin/env bash
ftp -n 92.168.1.4 2121 <<EOF
cd Study/Math
put ~/Documents/Math/lesson.pdf lesson.pdf
EOF

Since the ftp program reads its input from /dev/stdin, you can use a heredoc to define what should be passed from /dev/stdin

Answer 3

Okay, after User123 gave me a link, I finally solved my problem. So, I am giving my working script.

#!/bin/sh

HOST='192.168.1.4 2121'
USER='username_of_ftp'
PASSWD='password_of_ftp'

/usr/bin/ftp -n $HOST <<END_SCRIPT
user ${USER} ${PASSWD}
cd Study/Math
put ~/Documents/Math/lesson.pdf lesson.pdf
quit
END_SCRIPT

exit 0

Answer 4

While the ftp approach you're working with might be OK for your purposes, it's not going to behave properly if the server doesn't respond as expected.

As has already been suggested, use something other than ftp if at all possible. Scp or rsync using key authentication will work better, be more convenient since it won't break every time you change your password, and be more secure.