exploding string into individual characters using a shell script

farmerjoe · 10-11-2004, 10:38 AM

I am having trouble exploding a URL into a list of individual characters into a file using a linux bash script.

Example:
p.t.com >> Into:
p
.
t
.
c
o
m

I fiddled around with it yesterday and I guess i am having a brain malfuction. Can someone help me out? I'd be forever in your service.
Thanks,
famerjoe

theYinYeti · 10-11-2004, 10:42 AM

If there's no space in your URL, then maybe this:

Code:

echo "$URL" | sed 's|\([^[:space:]]\)|\1 |g' | sed 's| |\n|g'

Yves.

farmerjoe · 10-11-2004, 10:53 AM

thanks so much. Worked like a dream!

-farmerjoe

jlliagre · 10-11-2004, 03:46 PM

Quote:

echo "$URL" | sed 's|$[^[:space:]]$|\1 |g' | sed 's| |\n|g'

Or simpler:

Code:

echo "$URL"  | sed 's/./&\n/g'

theYinYeti · 10-12-2004, 03:16 AM

I like this!
But you're (unknowingly) pointing at something I've always wondered: If you write a sed rule like 's|(\something\)|\1 something|g' (note that something is *after* the \1, and the 'g' option), is there a risk on any platform, that sed will apply the same rule to the something that is after \1? Or will parsing go on with what is after the initial $something$ consistently on all platforms?
In short, is there a risk to write a rule that will infinitely recurse?

Yves.

jlliagre · 10-12-2004, 04:30 AM

Well, If such a bug existed, it would have manifested itself since 1978, where the first sed was made available (Unix version 7), and I'm not aware of that.

Another side note, both my answer and yours are in fact non portable, as they use a gnu extension allowing \n to be present in the replacement string.
With standard Unix sed, one should use something like:

Code:

echo "$URL"  | sed 's/./&\^J/g'

Where ^J is a real newline, entered as is or with the sequence control-V control-J.

PS: Il fait beau à Rennes ?

theYinYeti · 10-12-2004, 07:21 AM

Hi! Weather's changing from bright sunshine to heavy rain, and back, every 10 minutes! But à Rennes, je ne sais pas...

I'm very interested in that last bit (not the weather, the ^J

)
How did you know control-V control-J would do that?

Yves.

jlliagre · 10-12-2004, 12:23 PM

Je suis tombé dedans quand j'étais petit ...

theYinYeti · 10-13-2004, 02:59 AM

Ah... OK. (non French people: he fell into Unix when he still was a kid, reference to Obelix in the Asterix books)

Is there a man or web page where I could drink some of this magic knowledge?

jlliagre · 10-13-2004, 03:23 AM

man vi:
^V: quote non-printable character
man ksh/bash:
set -o
vi Use a vi-style command line editing interface.

Yes you have to read between the lines to know all of that ...