Assuming you are using bash release 4.0 or newer...

CODE=A

declare -A domain

domain=(
 [a]=com.tencent.ig
 [b]=com.vng.pubgmobile
 [c]=com.pubg.krmobile
 [d]=com.rekoo.pubgm
)

PN=$domain[$CODE,,]:?ERROR! CODE KOSONG, MELAKUKAN EXIT OTOMATIS

In the code, I define an associative array containing all the domain names, each associated with a single letter lower-case key.

The $PN variable is assigned the domain name corresponding to the lower-cased $CODE value ($CODE,, returns the value of $CODE turned into lower case letters only) from this array, but if the $CODE does not correspond to a valid entry in the domain list, it exits the script with an error.

The $variable:?error message parameter substitution would expand to the value of $variable (the appropriate domain in the code) but would exit the script with the error message if the value is empty not available. You don't get exactly the same formatting of the error message as in your code, but it would essentially behave the same if $CODE is invalid:

$ bash script.sh
script.sh: line 12: domain[$CODE,,]: ERROR! CODE KOSONG, MELAKUKAN EXIT OTOMATIS

If you care about character count, we can shorten this further:

CODE=A
declare -A domain=( [a]=tencent.ig [b]=vng.pubgmobile [c]=pubg.krmobile [d]=rekoo.pubgm )
PN=com.$domain[$CODE,,]:?ERROR! CODE KOSONG, MELAKUKAN EXIT OTOMATIS

Apart from deleting unnecessary newlines, I've also removed com. from each domain (this is instead added in the assignment to PN).

Note that all code above would work even for a multi-character value in $CODE (if lower-cased keys existed for these in the domain array).

If $CODE was a numerical (zero-based) index instead, this would simplify the code a bit:

CODE=0

domain=( com.tencent.ig com.vng.pubgmobile com.pubg.krmobile com.rekoo.pubgm )
PN=$domain[CODE]:?ERROR! CODE KOSONG, MELAKUKAN EXIT OTOMATIS

This would additionally make it really easy to read the domain array from an auxiliary file containing one entry per line:

CODE=0

readarray -t domain <domains.txt
PN=$domain[CODE]:?ERROR! CODE KOSONG, MELAKUKAN EXIT OTOMATIS

If your shell allow arrays, the shortest answer should be like this example in bash:

declare -A site
site=( [a]=com.tencent.ig [b]=com.vng.pubgmobile [c]=com.pubg.krmobile [d]=com.rekoo.pubgm )

pn=$site[$code,]

That is assuming that $code could only be a, b, c or d.

If not, add a test like:

case $site, in
 a|b|c|d) pn=$site[$code,];;
 *) pn="default site"
 printf 'at %sn' 'ERROR!' 'CODE KOSONG' 'MELAKUKAN EXIT OTOMATIS'
 exit 1
 ;;
esac

I'm going to take this answer a different direction. Rather than coding your data into the script, put that data into a separate data file, then use code to search the file:

$ cat names.cfg 
a com.tencent.ig
b com.vng.pubgmobile
c com.pubg.krmobile
d com.rekoo.pubgm

$ cat lookup.sh
PN=$(awk -v code="$1:-" 'tolower($1) == tolower(code) print $2; ' names.cfg)
if [ -z "$PN" ]; then
 printf 'at%sn' 'ERROR!' 'CODE KOSONG' 'MELAKUKAN EXIT OTOMATIS' >&2
 exit 1
fi
echo "$PN"

$ bash lookup.sh A
com.tencent.ig
$ bash lookup.sh a
com.tencent.ig
$ bash lookup.sh x
 ERROR!
 CODE KOSONG
 MELAKUKAN EXIT OTOMATIS

Separating these concerns has a few benefits:

• Add and remove data easily and simply, without having to work around code logic.


• Other programs can reuse the data, like counting how many matches are in a particular sub domain.


• If you have a huge list of data, you can sort it on disk and use look to efficiently binary search it (rather than line-by-line grep or awk)

You are using letters to index the values, if you were to use numbers, it becomes as simple as:

code=1
set -- com.tencent.ig com.vng.pubgmobile com.pubg.krmobile com.rekoo.pubgm

eval pn=$"$code"

That's portable shell code, will work on most shells.

For bash you may use: pn=$!code, or for bash/ksh/zsh use: pn=$@:code:1.

letters

If you must user letters (from a to z, or A to Z) they must be converted to an index:

code=a # or A, B, C, ... etc.
set -- com.tencent.ig com.vng.pubgmobile com.pubg.krmobile com.rekoo.pubgm
eval pn="$32)-96 ))"

In a longer code to clarify the intent and meaning of each part:

code=A

set -- com.tencent.ig com.vng.pubgmobile com.pubg.krmobile com.rekoo.pubgm

asciival=$(( $(printf '%d' "'$code") )) # byte value of the ASCII letter.
upperval=$(( asciival | 32 )) # shift to uppercase.
indexval=$(( upperval - 96 )) # convert to an index from a=1.
eval arg="$$indexval" # the argument at such index.

If you need to convert to lowercase values, use: $(( asciival & ~32 )) (make sure that bit 6 of the ascii value is unset).

error code

The output that your script prints on an error is quite long (and particular).

The most versatile way to deal with it is to define a function:

errorcode() exitcode=$1; shift; printf 'at %sn' "$@"; exit "$exitcode"; 

And then call that function with the specific message(s) you need.

errorcode 27 "ERROR!" "CODE KOSONG" "MELAKUKAN EXIT OTOMATIS"

Note that the resulting exit value is given by exitcode (example here is 27).

A full script (with error checking) then becomes:

errorcode() exitcode=$1; shift; printf 'at %sn' "$@"; exit "$exitcode"; 

code=$1:-A

case "$code" in 
 [a-d]|[A-D]) : ;;
 *) errorcode 27 "ERROR!" "CODE KOSONG" "MELAKUKAN EXIT OTOMATIS" ;;
esac

set -- com.tencent.ig com.vng.pubgmobile com.pubg.krmobile com.rekoo.pubgm
eval pn="$$(( ($(printf '%d' "'$code") & ~32) - 64 ))"

printf 'Code=%s Argument=%sn' "$code" "$pn"