How to get the current value of LC_CTYPE etc. in Bash?

Question

Basically, how to achieve this in Bash? Parsing the output of locale - declare "$(locale | grep ^LC_CTYPE | tr --delete '"')" - seems yucky, as it involves four separate commands. Remember, just because locale prints values for most or all variables doesn't mean those variables are actually set! For example, locale prints LC_CTYPE="en_NZ.UTF-8" (among other lines) on my machine, but echo "$LC_CTYPE" prints nothing.

Answer 1

Assuming evaluating the output of locale is safe (we assume that locale is not a shell function, alias, or other non-standard utility):

(eval "$(locale)" && printf '%s\n' "$LC_CTYPE")

This sets all the LC_ and associated variables in the subshell environment and outputs the value of the LC_CTYPE variable. Performing the eval inside the subshell avoids polluting the parent environment with the LC_ variables.

Example run on my OpenBSD system where I only ever set LANG=C.UTF-8:

$ (eval "$(locale)" && printf '%s\n' "$LC_CTYPE")
C.UTF-8

If you like to set (and export) the LC_CTYPE variable to the value reported by locale without setting other variables:

$ export LC_CTYPE="$(eval "$(locale)" && printf '%s\n' "$LC_CTYPE")"
$ printf '%s\n' "$LC_CTYPE"
C.UTF-8

Answer 2

According to man locale the value of LC_CTYPE being enclosed in double quotes signifies it's an "implied value":

Values for variables set in the environment are printed without
double quotes, implied values are printed with double quotes.

which means that LC_CTYPE is not set and locale will print the "implied" value which, if I understand correctly, will be the value of LC_ALL or, if that's not set either, the value of LANG:

For glibc, first (regardless of category), the environment variable LC_ALL is inspected, next the environment variable with the same name as the category, and finally the environment variable LANG. The first existing environment variable is used

So locale will use the first value it finds, in this order: LC_ALL, then LC_CTYPE and then LANG Note that LC_ALL takes precedence if set, so even if LC_CTYPE was set too (maybe to a different locale) locale will report the value of LC_ALL for LC_CTYPE.

In conclusion, to get the value of LC_CTYPE that is currently being used by locale you could run something like

echo ${LC_ALL:-${LC_CTYPE:-$LANG}}

---

Initially I had thought the goal was to get the actual value of LC_CTYPE if set and only if it's not set, fall back to what locale uses, in which case the first two variables have to be swapped:

echo ${LC_CTYPE:-${LC_ALL:-$LANG}}

Answer 3

If you just want to parse the output of locale and then set the variable, you can just source it directly like this:

. <(locale | grep '^LC_CTYPE=')

That selects only the LC_TYPE line:

$ locale | grep '^LC_CTYPE='
LC_CTYPE="en_US.UTF-8"

And then you source that, using the . builtin, into the current shell:

$ echo $LC_CTYPE 

$ . <(locale | grep '^LC_CTYPE=')
$ echo "$LC_CTYPE"
en_US.UTF-8

Note that this requires a shell that supports process substitution, such as bash or zsh or ksh and others. If you are not using such a shell, you might need to do something more complicated like

locale | grep '^LC_CTYPE=' > file && . ./file

Answer 4

Without using any external commands, except for locale:

while read -r line; do
    [[ "${line}" =~ ^LC_CTYPE= ]] && {
        export LC_CTYPE="${line#*=}"
        break
    }
done < <(locale)