Parsing

Go 13 Sep 2026 4 min read

Split Text with Custom Rune Boundaries Using strings.FieldsFunc in Go

strings.FieldsFunc treats selected Unicode code points as boundaries and returns the non-empty text between them. That behavior fits inputs where separators belong to a class rather than one fixed substring: commas and semicolons, several punctuation marks, or any rune accepted by a deterministic predicate. fields := strings.FieldsFunc(input, func(r rune) bool { return r == ',' || r == ';' }) For alpha,,beta;gamma;, the result is []string{"alpha", "beta", "gamma"}. Consecutive matching runes form a boundary region, and matching runes at either edge do not produce empty elements.

Golang Strings

Go 13 Sep 2026 4 min read

Split Once with strings.Cut in Go

strings.Cut separates a string around the first occurrence of a delimiter and reports whether that delimiter was present. That three-result contract matters in parsers where a missing separator is different from a separator followed by an empty value. before, after, found := strings.Cut(input, "=") When the separator exists, before contains the text preceding its first occurrence and after contains the remainder. When it does not exist, the function returns the original string, an empty second string, and false.

Golang Strings

Go 13 Sep 2026 4 min read

Remove Explicit Suffixes with strings.CutSuffix in Go

strings.CutSuffix removes one exact trailing string and reports whether that suffix was present. The boolean result is the key distinction from operations that only return transformed text: callers can keep suffix recognition separate from the remaining content. base, found := strings.CutSuffix(name, ".json") If name ends in .json, base contains the preceding text and found is true. Otherwise, base is the original string and found is false. The operation does not scan for a matching fragment in the middle and does not repeatedly strip the suffix.

Golang Strings