[xubuntu-users] dash - looping through alphabet

[Steve Litt]

On Sun, 06 Jul 2014 07:26:34 +0200
Ralf Mardorf <ralf.mardorf at rocketmail.com> wrote:

> On Sat, 2014-07-05 at 19:49 -0400, Steve Litt wrote:
> > I couldn't get anything to work without putting spaces between every
> > letter from a to z.
> 
> Thank you,
> 
> but if this is needed, then I don't want to use a loop, but do it this

Wouldn't blame you a bit, but I can make it much easier. Read on...

> >  Would you consider a C solution?
> 
> No, it should be a shell script and for this script I prefer dash over

OK, how bout a partial C solution that gives Unix a much-needed "do one
thing and do it well" command? The following rng executable takes a
single, two letter argument, and returns a space-delimited range
from the first letter to the second letter, inclusive:

=============================================================
#include<unistd.h>
int main(int argc, char *argv[]){
	char buf[10];
	char start = argv[1][0];
	char end = argv[1][1];
	char i;
	for(i=start; i <= end; i++){
		buf[0] = i;
		write(1, buf, 1);
		if(i < end)
			write(1, " ", 1);
	}
	return 0;
}
=============================================================

Because the preceding doesn't include <stdio.h>, it's fairly small,
6854 bytes. So rng eg returns "e f g".

So, when you iterate in your shellscript, do this:

=============================================================
#!/bin/dash

for c in `./rng az`; do
	echo $c
	# Do whatever else with $c
done
=============================================================

Works equally well in dash and bash. Obviously, in real life you put
rng in a directory on the path and get rid of the "./".

As far as pure shellscript solutions, I tried a lot of things,
including the well documented and highly spoken of:

printf "%03o" ascii_number

and none worked. The "%03o" thing just printed the number again.

Unix really should have a chr command. Rather than making a chr
command, I just made a rng command that makes your shellscript loop
logic trivial.

SteveT

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