1LEXGROG(1) Manual pager utils LEXGROG(1)
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6 lexgrog - parse header information in man pages
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9 lexgrog [-m|-c] [-fhwV] [-E encoding] file ...
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12 lexgrog is an implementation of the traditional “groff guess” utility
13 in lex. It reads the list of files on its command line as either man
14 page source files or preformatted “cat” pages, and displays their name
15 and description as used by apropos and whatis, the list of preprocess‐
16 ing filters required by the man page before it is passed to nroff or
17 troff, or both.
18 If its input is badly formatted, lexgrog will print “parse failed”;
20 this may be useful for external programs that need to check man pages
21 for correctness. If one of lexgrog's input files is “-”, it will read
22 from standard input; if any input file is compressed, a decompressed
23 version will be read automatically.
24
26 -m, --man
27 Parse input as man page source files. This is the default if
28 neither --man nor --cat is given.
29 -c, --cat
31 Parse input as preformatted man pages (“cat pages”). --man and
32 --cat may not be given simultaneously.
33 -w, --whatis
35 Display the name and description from the man page's header, as
36 used by apropos and whatis. This is the default if neither
37 --whatis nor --filters is given.
38 -f, --filters
40 Display the list of filters needed to preprocess the man page
41 before formatting with nroff or troff.
42 -E encoding, --encoding encoding
44 Override the guessed character set for the page to encoding.
45 -h, --help
47 Print a help message and exit.
48 -V, --version
50 Display version information.
51
53 0 Successful program execution.
54 1 Usage error.
56 2 lexgrog failed to parse one or more of its input files.
58
60 $ lexgrog man.1
61 man.1: "man - an interface to the on-line reference manuals"
62 $ lexgrog -fw man.1
63 man.1 (t): "man - an interface to the on-line reference manuals"
64 $ lexgrog -c whatis.cat1
65 whatis.cat1: "whatis - display manual page descriptions"
66 $ lexgrog broken.1
67 broken.1: parse failed
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70 mandb (which uses the same code as lexgrog) parses the NAME section at
71 the top of each manual page looking for names and descriptions of the
72 features documented in each. While the parser is quite tolerant, as it
73 has to cope with a number of different forms that have historically
74 been used, it may sometimes fail to extract the required information.
75 When using the traditional man macro set, a correct NAME section looks
77 something like this:
78 .SH NAME
80 foo \- program to do something
81 Some manual pagers require the ‘\-’ to be exactly as shown; mandb is
83 more tolerant, but for compatibility with other systems it is neverthe‐
84 less a good idea to retain the backslash.
85 On the left-hand side, there may be several names, separated by commas.
87 Names containing whitespace will be ignored to avoid pathological be‐
88 haviour on certain ill-formed NAME sections. The text on the right-
89 hand side is free-form, and may be spread over multiple lines. If sev‐
90 eral features with different descriptions are being documented in the
91 same manual page, the following form is therefore used:
92 .SH NAME
94 foo, bar \- programs to do something
95 .br
96 baz \- program to do nothing
97 (A macro which starts a new paragraph, like .PP, may be used instead of
99 the break macro .br.)
100 When using the BSD-derived mdoc macro set, a correct NAME section looks
102 something like this:
103 .Sh NAME
105 .Nm foo
106 .Nd program to do something
107 There are several common reasons why whatis parsing fails. Sometimes
109 authors of manual pages replace ‘.SH NAME’ with ‘.SH MYPROGRAM’, and
110 then mandb cannot find the section from which to extract the informa‐
111 tion it needs. Sometimes authors include a NAME section, but place
112 free-form text there rather than ‘name \- description’. However, any
113 syntax resembling the above should be accepted.
114
116 man(1), mandb(8), apropos(1), whatis(1).
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119 lexgrog attempts to parse files containing .so requests, but will only
120 be able to do so correctly if the files are properly installed in a
121 manual page hierarchy.
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124 The code used by lexgrog to scan man pages was written by:
125 Wilf. (G.Wilford@ee.surrey.ac.uk).
127 Fabrizio Polacco (fpolacco@debian.org).
128 Colin Watson (cjwatson@debian.org).
129 Colin Watson wrote the current incarnation of the command-line front-
131 end, as well as this man page.
1322.5.7 2010-02-16 LEXGROG(1)