Leaders (The GNU Troff Manual)

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5.12.1 Leaders

+ + +

Sometimes it is desirable to fill a tab stop with a given glyph, +but also use tab stops normally on the same output line. An example is +a table of contents entry that uses dots to bridge the entry name with +its page number, which is itself aligned between tab stops. The +roff language provides leaders for this +purpose.⁶⁷ +

+ +

A leader character (ISO and EBCDIC code +point 1, also known as SOH or “start of heading”), +behaves similarly to a tab character: it moves to the next tab stop. +The difference is that for this movement, the default fill character is +a period ‘.’. +

Escape sequence: \a ¶: + + + + + +
Interpolate a leader in copy mode; see Copy Mode. +

+ +

Request: .lc [c] ¶: + + + +
Set the leader repetition character to the ordinary or special character +c. Recall Tabs and Leaders: when encountering a leader +character in the input, the formatter writes as many dots ‘.’ as +are necessary until +reaching the next tab stop; this is the leader definition +character. Omitting c unsets the leader +character. With no argument, GNU troff treats leaders the same +as tabs. The leader repetition character is associated with the +environment (see Environments). Only a single c is +recognized; any excess is ignored. +

+ + + +

A table of contents, for example, may define tab stops after a section +number, a title, and a gap to be filled with leader dots. The page +number follows the leader, after a right-aligned final tab stop wide +enough to house the largest page number occurring in the document. +

.ds entry1 19.\tThe Prophet\a\t98
+.ds entry2 20.\tAll Astir\a\t101
+.ta .5i 4.5i +.5iR
+.nf
+\*[entry1]
+\*[entry2]
+    ⇒ 19.  The Prophet.............................   98
+    ⇒ 20.  All Astir...............................  101
+

+ + +