substringAfterLast
Returns a substring after the last occurrence of delimiter. If the string does not contain the delimiter, returns missingDelimiterValue which defaults to the original string.
fun String.substringAfterLast(delimiter: Char, missingDelimiterValue: String = this): String(source)
val path = "/home/user/docs/file.txt"
val fileName = path.substringAfterLast('/')
println(fileName) // prints: file.txt
val plain = "filename".substringAfterLast('/', "no delimiter")
println(plain) // prints: filename