How to check if `wget` supports a certain feature programatically?

Question

Is there a way to programatically detect if the currently installed wget supports a given feature, for example, IRI support?

I’m asking because I’d like to add these lines to my .wgetrc:

# Use UTF-8 as the default system encoding
local_encoding = UTF-8

But this makes wget unusable if it doesn’t support the local_encoding setting.

So, I’d like to conditionally configure this setting, only if wget supports the feature.

In Vim (.vimrc files) you can do this using has() and exists():

if has("autocmd")
  " Define autocommands here
endif

How can I do something similar for wget in .wgetrc?

Answer 1

What about this in some shell initialization script?

if wget --help | grep -q "local-encoding"; then 
    # modify ~/.wgetrc
fi

Answer 2

You cannot include any extra logic into .wgetrc, so using shell initialization as described in enzotib's answer seems to be the only possibility.

Beside of --help, you can get the build configuration of GNU’s wget and therefore the enabled features via --version:

if wget --version | grep -q "+iri"; then 
    # modify ~/.wgetrc
fi

In the case you need to test if a feature is also included in busybox’s wget, you need to know that is does not support --version and prints instead its "--help" to stderr (not stdout as GNU’s wget).