5.5.3 Escapes

Escapes may occur anywhere in the input to gtroff. They usually begin with a backslash and are followed by a single character, which indicates the function to be performed. The escape character can be changed; see Character Translations.

Escape sequences that require an identifier as a parameter accept three possible syntax forms.

• The next single character is the identifier.
• If this single character is an opening parenthesis, take the following two characters as the identifier. Note that there is no closing parenthesis after the identifier.
• If this single character is an opening bracket, take all characters until a closing bracket as the identifier.

Examples:

\fB
\n(XX
\*[TeX]

Other escapes may require several arguments and/or some special format. In such cases the argument is traditionally enclosed in single quotes (and quotes are always used in this manual for the definitions of escape sequences). The enclosed text is then processed according to what that escape expects. Example:

\l'1.5i\(bu'

Note that the quote character can be replaced with any other character that does not occur in the argument (even a newline or a space character) in the following escapes: \o, \b, and \X. This makes e.g.

A caf
\o
e\'


in Paris
  ⇒ A café in Paris

possible, but it is better not to use this feature to avoid confusion.

The following escapes sequences (which are handled similarly to characters since they don’t take a parameter) are also allowed as delimiters: \%, ‘\ ’, \|, \^, \{, \}, \', \`, \-, \_, \!, \?, \), \/, \,, \&, \:, \~, \0, \a, \c, \d, \e, \E, \p, \r, \t, and \u. Again, don’t use these if possible.

No newline characters as delimiters are allowed in the following escapes: \A, \B, \Z, \C, and \w.

Finally, the escapes \D, \h, \H, \l, \L, \N, \R, \s, \S, \v, and \x can’t use the following characters as delimiters:

• The digits 0-9.
• The (single-character) operators ‘+-/*%<>=&:().’.
• The space, tab, and newline characters.
• All escape sequences except \%, \:, \{, \}, \', \`, \-, \_, \!, \/, \c, \e, and \p.

To have a backslash (actually, the current escape character) appear in the output several escapes are defined: \\, \e or \E. These are very similar, and only differ with respect to being used in macros or diversions. See Character Translations, for an exact description of those escapes.

See Implementation Differences, Copy-in Mode, and Diversions, Identifiers, for more information.