Split a string to print first two characters delimited by "-" In Bash - bash

Question

I am listing the AWS region names.
us-east-1
ap-southeast-1
I want to split the string to print specific first characters delimited by - i.e. 'two characters'-'one character'-'one character'. So us-east-1 should be printed as use1 and ap-southeast-1 should be printed as aps1
I have tried this and it's giving me expected results. I was thinking if there is a shorter way to achieve this.
region=us-east-1
regionlen=$(echo -n $region | wc -m)
echo $region | sed 's/-//' | cut -c 1-3,expr $regionlen - 2-expr $regionlen - 1

Answer 1

How about using sed:
echo "$region" | sed -E 's/^(.[^-]?)[^-]*-(.)[^-]*-(.).*$/\1\2\3/'
Explanation: the s/pattern/replacement/ command picks out the relevant parts of the region name, replacing the entire name with just the relevant bits. The pattern is:
^ - the beginning of the string
(.[^-]?) - the first character, and another (if it's not a dash)
[^-]* - any more things up to a dash
- - a dash (the first one)
(.) - The first character of the second word
[^-]*- - the rest of the second word, then the dash
(.) - The first character of the third word
.*$ - Anything remaining through the end
The bits in parentheses get captured, so \1\2\3 pulls them out and replaces the whole thing with just those.

Answer 2

IFS influencing field splitting step of parameter expansion:
$ str=us-east-2
$ IFS=- eval 'set -- $str'
$ echo $#
3
$ echo $1
us
$ echo $2
east
$ echo $3
No external utilities; just processing in the language.
This is how smartly written build configuration scripts parse version numbers like 1.13.4 and architecture strings like i386-gnu-linux.
The eval can be avoided, if we save and restore IFS.
$ save_ifs=$IFS; set -- $str; IFS=$save_ifs

Answer 3

Using bash, and assuming that you need to distinguish between things like southwest and southeast:
s=ap-southwest-1
a=${s:0:2}
b=${s#*-}
b=${b%-*}
c=${s##*-}
bb=
case "$b" in
south*) bb+=s ;;&
north*) bb+=n ;;&
*east*) bb+=e ;;
*west*) bb+=w ;;
esac
echo "$a$bb$c"

Answer 4

How about:
region="us-east-1"
echo "$region" | (IFS=- read -r a b c; echo "$a${b:0:1}${c:0:1}")
use1

Answer 5

A simple sed -
$: printf "us-east-1\nap-southeast-1\n" |
sed -E 's/-(.)[^-]*/\1/g'
To keep noncardinal specifications like southeast distinct from south at the cost of adding an optional additional character -
$: printf "us-east-1\nap-southeast-1\n" |
sed -E '
s/north/n/;
s/south/s/;
s/east/e/;
s/west/w/;
s/-//g;'
If you could have south-southwest, add g to those directional reductions.
if you MUST have exactly 4 characters of output, I recommend mapping the eight or 16 map directions to specific characters, so that north is N, northeast is maybe O and northwest M... that sort of thing.