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ABNF Core Rules (RFC5234 B.1.)
Functions
- ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
- BIT = “0” / “1”
- CHAR = %x01-7F ; any 7-bit US-ASCII character, excluding NUL
- Carriage return
- Internet standard newline
- Newline, with and without “\r”.
- CTL = %x00-1F / %x7F ; controls
- DIGIT = %x30-39 ; 0-9
- Double Quote
- HEXDIG = DIGIT / “A” / “B” / “C” / “D” / “E” / “F”
- Horizontal tab
- Linefeed
- Use of this linear-white-space rule permits lines containing only white space that are no longer legal in mail headers and have caused interoperability problems in other contexts.
- OCTET = %x00-FF ; 8 bits of data
- SP = %x20
- VCHAR = %x21-7E ; visible (printing) characters
- White space