How to compare two string values in Go in a case insensitive manner?

Question

How to compare two strings with case insensitivity? For example: Both "a" == "a" and "a" == "A" must return true.

what's the meaning of asking a question then answering it in less than 6 min ? — Chiheb Nexus, May 17 '17 at 23:57
Possible duplicate of [Case insensitive string search in golang](http://stackoverflow.com/questions/24836044/case-insensitive-string-search-in-golang) — WiredPrairie, May 18 '17 at 10:34

score 27 · Answer 1 · answered May 17 '17 at 23:59

27

There is a strings.EqualFold() function which performs case insensitive string comparison.

For example:

fmt.Println(strings.EqualFold("aa", "Aa"))
fmt.Println(strings.EqualFold("aa", "AA"))
fmt.Println(strings.EqualFold("aa", "Ab"))

Output (try it on the Go Playground):

true
true
false

answered May 17 '17 at 23:59

icza

389,944
63
907
827

2

Note: assumes `utf-8`. – Dean Coakley Nov 29 '18 at 09:16

score -1 · Answer 2 · answered May 17 '17 at 23:53

-1

Found the answer. Convert both strings to either lowercase or upper case and compare. import "strings" strings.ToUpper(str1) == strings.ToUpper(str2)

answered May 17 '17 at 23:53

Prasanna

101
1
3

2

Converting strings to lowercase or uppercase only gives an approximately correct result - Unicode isn't this simple. Research the "Turkish i" problem for a starting point on diving down the rabbithole. – Bevan May 01 '20 at 04:58

score -2 · Answer 3 · answered Mar 12 '20 at 15:15

strings.EqualFold() is not compare, some times you need sign of compare

func compareNoCase(i, j string) int {
    is, js := []rune(i), []rune(j)
    il, jl := len(is), len(js)

  ml := il
    if ml > jl {
        ml = jl
    }

    for n := 0; n < ml; n++ {
        ir, jr := unicode.ToLower(is[n]), unicode.ToLower(js[n])
        if ir < jr {
            return -1
        } else if ir > jr {
            return 1
        }
    }

    if il < jl {
        return -1
    }
    if il > jl {
        return 1
    }
    return 0
}

func equalsNoCase(i, j string) bool {
    return compareNoCase(i, j) == 0
}

How to compare two string values in Go in a case insensitive manner?

3 Answers3