# grex > Generate regular expressions. > More information: . - Generate a simple regular expression: `grex {{space_separated_strings}}` - Generate a case-insensitive regular expression: `grex {{[-i|--ignore-case]}} {{space_separated_strings}}` - Replace digits with '\d': `grex {{[-d|--digits]}} {{space_separated_strings}}` - Replace Unicode word character with '\w': `grex {{[-w|--words]}} {{space_separated_strings}}` - Replace spaces with '\s': `grex {{[-s|--spaces]}} {{space_separated_strings}}` - Add {min, max} quantifier representation for repeating sub-strings: `grex {{[-r|--repetitions]}} {{space_separated_strings}}`