I was wondering what is the proper way to test whether a substring is included in some other string. If I want to check if string a is part of string b, I'm currently using

matchstr(b, a) != ""

to check if a is a substring of b. Is there a more "proper" way of doing it, since this seems like a bit of a hack.

  • 1
    You can not use matchstr like this, 2nd arg of matchstr is a regex pattern, eg: matchstr('ab', '.') will return 'a'.
    – dedowsdi
    Apr 19, 2019 at 5:01
  • @dedowsdi valid comment. This might be relevant to other users, but in my case these strings are guaranteed to not contain regex. Apr 19, 2019 at 5:04

2 Answers 2


For this there is the function stridx().

let a = "Vi and Vim"
let b = "and"
echo stridx(a, b)
" echos 3

If the substring is not found stridx() returns -1. The function also supports a third argument to specify the start index to search from.

See :help stridx().

  • 2
    If you want to accept a match anywhere in the string, including the start of the string, then use if stridx(a, b) >= 0 Dec 27, 2020 at 4:32

There's an even easier way in at least version 8.x which I've been using for some time:

if hostname() =~ ''

which is a simple regex match expression with ignorecase. Here's the section from the Vim manual that explains comparisons, which includes this operator.

expr5 {cmp} expr5

Compare two expr5 expressions, resulting in a 0 if it evaluates to false, or 1
if it evaluates to true.

                 use 'ignorecase'    match case    ignore case ~
regexp matches           =~             =~#             =~?
regexp doesn't match    !~              !~#             !~?

And as pointed out by Big McLargeHuge in the comment, the specific form in this case is

<string-to-test> =~ <regex-pattern>
  • 1
    To clarify, the pattern goes on the RHS. So if you want to test if string a is part of string b, you'd use b =~ a. May 21, 2021 at 2:47

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