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Reputation: 5082

How to evaluate if a environment variable is set in vimrc

How to evaluate if an bash environment variable is set

for example 

function! Myfoo(arg)
  if $SomeVar is set/exist ----> how to eval the SomeVar has been set
     ....
  endif
endfunction

Upvotes: 18

Views: 6557

Answers (1)

Ingo Karkat
Ingo Karkat

Reputation: 172590

You've (intuitively?) used the correct syntax; as :help expression-syntax explains (under :help expr-env), the syntax is $VAR.

You can compare with an empty string (if $SomeVar != "") or use empty() (if !empty($SomeVar)) to check whether a (non-empty) value has been supplied. It's not so easy to differentiate between empty environment variable and non-existing environment variable, so this is best avoided. (This distinction also is rarely used in shell scripts itself, neither.)

Example:

# vi ~/.vimrc
if !empty($vim_background)
   :let &background = $vim_background
endif

Upvotes: 27

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