How to check if a string is a substring of another string

Question

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.

Answer 1

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().

Answer 2

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

if hostname() =~ '10.12.12.132'

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>