Rx

let space = /[ \t]+/

A mandatory space or tab

let opt_space = /[ \t]*/

An optional space or tab

let cl = /[ \t]*\\\\\n[ \t]*/

A continued line with a backslash

let cl_or_space = cl | space

A cl or a space

let cl_or_opt_space = cl | opt_space

A cl or a opt_space

let space_in = /[^ \r\t\n].*[^ \r\t\n]|[^ \t\n\r]/

A string which not starting or ending with a space

let no_spaces = /[^ \t\r\n]+/

A string with no spaces

let word = /[A-Za-z0-9_.-]+/

An alphanumeric string

let integer = /[0-9]+/

One or more digits

let relinteger = /[-+]?[0-9]+/

A relative integer

let relinteger_noplus = /[-]?[0-9]+/

A relative integer, without explicit plus sign

let decimal = /[0-9]+([.,][0-9]+)?/

A decimal value (using ‘,’ or ‘.’ as a separator)

let reldecimal = /[+-]?[0-9]+([.,][0-9]+)?/

A relative decimal

let byte = /25[0-5]?|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9]/

let hex = /0x[0-9a-fA-F]+/

A hex value

let octal = /0[0-7]+/

An octal value

let fspath = /[^ \t\n]+/

A filesystem path

let neg1 = /[^,# \n\t]+/

Anything but a space, a comma or a comment sign

let ipv4 = let dot = "." in byte . dot . byte . dot . byte . dot . byte

let ipv6 = /(([0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4})/ | /(([0-9A-Fa-f]{1,4}:){6}:[0-9A-Fa-f]{1,4})/ | /(([0-9A-Fa-f]{1,4}:){5}:([0-9A-Fa-f]{1,4}:)?[0-9A-Fa-f]{1,4})/ | /(([0-9A-Fa-f]{1,4}:){4}:([0-9A-Fa-f]{1,4}:){0,2}[0-9A-Fa-f]{1,4})/ | /(([0-9A-Fa-f]{1,4}:){3}:([0-9A-Fa-f]{1,4}:){0,3}[0-9A-Fa-f]{1,4})/ | /(([0-9A-Fa-f]{1,4}:){2}:([0-9A-Fa-f]{1,4}:){0,4}[0-9A-Fa-f]{1,4})/ | ( /([0-9A-Fa-f]{1,4}:){6}/ . /((((25[0-5])|(1[0-9]{2})|(2[0-4][0-9])|([0-9]{1,2})))\.){3}/ . /(((25[0-5])|(1[0-9]{2})|(2[0-4][0-9])|([0-9]{1,2})))/ ) | ( /([0-9A-Fa-f]{1,4}:){0,5}:/ . /((((25[0-5])|(1[0-9]{2})|(2[0-4][0-9])|([0-9]{1,2})))\.){3}/ . /(((25[0-5])|(1[0-9]{2})|(2[0-4][0-9])|([0-9]{1,2})))/ ) | ( /::([0-9A-Fa-f]{1,4}:){0,5}/ . /((((25[0-5])|(1[0-9]{2})|(2[0-4][0-9])|([0-9]{1,2})))\.){3}/ . /(((25[0-5])|(1[0-9]{2})|(2[0-4][0-9])|([0-9]{1,2})))/ ) | ( /[0-9A-Fa-f]{1,4}::([0-9A-Fa-f]{1,4}:){0,5}/ . /[0-9A-Fa-f]{1,4}/ ) | /(::([0-9A-Fa-f]{1,4}:){0,6}[0-9A-Fa-f]{1,4})/ | /(([0-9A-Fa-f]{1,4}:){1,7}:)/

let ip = ipv4 | ipv6

An ipv4 or ipv6

let hostname = /(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*( [A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])/

A valid RFC 1123 hostname

let device_name = /[a-zA-Z0-9_?.+:!-]+/

A Linux device name like eth0 or i2c-0.  Might still be too restrictive

let email_addr = /[A-Za-z0-9_+.-]+@[A-Za-z0-9_.-]+/

To be refined

ISO 8601 date time format