mjhjmtu

I'm running iwlist wlo1 scan | grep ESSID inside a script.

It displays French characters in the following format

xC3x89 for É and xC3xA9 for é.

I'm not sure what this format is called. I tried using an answer for converting unicode echo -ne 'xC3xA9' | iconv -f utf-16be but it converted to 쎩.

What is the official name for this format and how can I convert it in bash?

Hexdecimal numeric constants are usually represented with 0x prefix.
Character and string constants may express character codes in hexadecimal with the prefix x followed by two hex digits.

echo -ne 'xC3x89' should give you É.

• 
  -e - enable interpretation of backslash escapes(including xHH - byte with hexadecimal value HH (1 to 2 digits))

To deal with better portability use printf function:

printf "%b" 'xC3x89'
É

Try

 % echo -n éÉ | hd
 00000000 c3 a9 c3 89 |....|
 00000004

where hd is the hexdump utility.

So your thing is just UTF-8 encoding (and your observed output xC3x89 is the hexadecimal representation of UTF-8). Today we have UTF-8 everywhere.

My environment has both LANG=en_US.UTF-8 and LC_ALL=en_US.UTF-8 (even if I am French).

Also,

echo 'xC3x89xC3xA9'

produces

Éé

as expected.

And so does

echo "\xC3\x89\xC3\xA9" | iconv -t utf-8

Read also locale(7).

Notice that some character encodings (e.g. old plain ASCII) don't have any é or É characters, and others (e.g. ISO-8859-1) encode them differently.

iwlist displays all the bytes that don't correspond to ASCII non-control characters as the xHH where HH is the byte number in hexadecimal.

To undo that encoding, you can pipe the output of iwlist to

perl -pe 's/\x([da-f]2)/chr(hex($1))/gie'

Byte 0xc3 followed by 0xa9 make up the UTF-8 encoding of the é character.

If your locale also uses the UTF-8 encoding, then the output of perl will show that é character. If not (unlikely as UTF-8 is the norm), you can always pipe the output of perl to iconv -f utf-8 to convert it from UTF-8 to the character encoding used in your locale.