Automating FTP I: UNIX and Linux

Having gotten tired of repeated typing in everything at the prompt of an interactive command line FTP session and doing similar things via GUI route, I started to wonder if there was a scripting alternative and, lo and behold, I found it after a spot of googling. There are various opportunities for its extension such as prompting for user name and password instead of the risky approach of including them in a script or cycling through a directory structure but here’s the foundation stone for such tinkering anyway:

HOSTNAME=’ftp.server.host’
USER=’user’
PSSWD=’password’
REP_SRC=’source_directory’
REP__DEST=’destination_directory’
FILENAME=’*’

rm -rf log_file.tmp

cd "${REP_DEST}"

ftp -i -n -v <<EndFTP >>log_file.tmp 2>>log_file.tmp
open ${HOSTNAME}
user ${USER} ${PSSWD}
prompt
cd "${REP_SRC}"
mget "${FILENAME}"
EndFTP

cd ~

Filename autocompletion on the command line

The Windows 2000 command line feels an austere primitive when compared with the wonders of the UNIX/Linux equivalent. Windows XP feels a little better and PowerShell is another animal altogether. With the latter pair, you do get file or folder autocompletion upon hitting the TAB key. What I didn’t realise until recently was that continued tabbed cycled through the possibilities; I was hitting it once and retyping when I got the wrong folder or file. I stand corrected. With the shell in Linux/UNIX, you can get a listing of possibilities when you hit TAB for the second time and the first time only gives you completion as far as it can go with certainty; you’ll never get to the wrong place but you may not get anywhere at all. This works for bash but not ksh88 as far as I can see. It’s interesting how you can take two different approaches in order to reach the same end.

On numeric for loops in Korn shell scripting

The time hounoured syntax for a for loop in a UNIX script is what you see below and that is what works with the default shell in Sun’s Solaris UNIX operating system, ksh88.

for i in 1 2 3 4 5 6 7 8 9 10
do
        if [[ -d dir$i ]]
        then
            :
        else
            mkdir dir$i
        fi
done

There is a much nicer syntax supported syntax the advent of ksh93. It follows C language conventions found in all sorts of places like Java, Perl, PHP and so on. Here is an example:

for (( i=1; i<11; i++ ))
do
        if [[ -d dir$i ]]
        then
            :
        else
            mkdir dir$i
       fi
done

Recalling previous commands in the Korn shell

The default shell on Solaris boxes seems to be Korn and the version that I have encountered doesn’t appear to allow obvious access to the command history. In the bash shell, the up and down cursor keys scroll through your command history for you but Korn doesn’t seem to allow this. Thankfully, there is another way: you can set up the editor vi as the default method for gaining access to the command history by adding the following line to the .profile file in your home directory:

set -o vi

Then, you can use the Vi (it’s pronounced vee-eye, apparently) commands ESC+h and ESC+j to move up and down the list of previous commands. That, or, assuming that you have access to it, just use the bash shell anyway…