flex: Flex flex: flex: Flex is a tool for generating scanners. A scanner, sometimes called a flex: tokenizer, is a program which recognizes lexical patterns in text. The flex: flex program reads user-specified input files, or its standard input if flex: no file names are given, for a description of a scanner to generate. The flex: description is in the form of pairs of regular expressions and C code, flex: called rules. flex: flex: flex: