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] [-dfw?V] [-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 -d, --debug
27 Print debugging information.
28 -m, --man
30 Parse input as man page source files. This is the default if
31 neither --man nor --cat is given.
32 -c, --cat
34 Parse input as preformatted man pages (“cat pages”). --man and
35 --cat may not be given simultaneously.
36 -w, --whatis
38 Display the name and description from the man page's header, as
39 used by apropos and whatis. This is the default if neither
40 --whatis nor --filters is given.
41 -f, --filters
43 Display the list of filters needed to preprocess the man page
44 before formatting with nroff or troff.
45 -E encoding, --encoding encoding
47 Override the guessed character set for the page to encoding.
48 -?, --help
50 Print a help message and exit.
51 --usage
53 Print a short usage message and exit.
54 -V, --version
56 Display version information.
57
59 0 Successful program execution.
60 1 Usage error.
62 2 lexgrog failed to parse one or more of its input files.
64
66 $ lexgrog man.1
67 man.1: "man - an interface to the system reference manuals"
68 $ lexgrog -fw man.1
69 man.1 (t): "man - an interface to the system reference manuals"
70 $ lexgrog -c whatis.cat1
71 whatis.cat1: "whatis - display manual page descriptions"
72 $ lexgrog broken.1
73 broken.1: parse failed
74
76 mandb (which uses the same code as lexgrog) parses the NAME section at
77 the top of each manual page looking for names and descriptions of the
78 features documented in each. While the parser is quite tolerant, as it
79 has to cope with a number of different forms that have historically
80 been used, it may sometimes fail to extract the required information.
81 When using the traditional man macro set, a correct NAME section looks
83 something like this:
84 .SH NAME
86 foo \- program to do something
87 Some manual pagers require the ‘\-’ to be exactly as shown; mandb is
89 more tolerant, but for compatibility with other systems it is neverthe‐
90 less a good idea to retain the backslash.
91 On the left-hand side, there may be several names, separated by commas.
93 Names containing whitespace will be ignored to avoid pathological be‐
94 haviour on certain ill-formed NAME sections. The text on the right-
95 hand side is free-form, and may be spread over multiple lines. If sev‐
96 eral features with different descriptions are being documented in the
97 same manual page, the following form is therefore used:
98 .SH NAME
100 foo, bar \- programs to do something
101 .br
102 baz \- program to do nothing
103 (A macro which starts a new paragraph, like .PP, may be used instead of
105 the break macro .br.)
106 When using the BSD-derived mdoc macro set, a correct NAME section looks
108 something like this:
109 .Sh NAME
111 .Nm foo
112 .Nd program to do something
113 There are several common reasons why whatis parsing fails. Sometimes
115 authors of manual pages replace ‘.SH NAME’ with ‘.SH MYPROGRAM’, and
116 then mandb cannot find the section from which to extract the informa‐
117 tion it needs. Sometimes authors include a NAME section, but place
118 free-form text there rather than ‘name \- description’. However, any
119 syntax resembling the above should be accepted.
120
122 apropos(1), man(1), whatis(1), mandb(8)
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125 lexgrog attempts to parse files containing .so requests, but will only
126 be able to do so correctly if the files are properly installed in a
127 manual page hierarchy.
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130 The code used by lexgrog to scan man pages was written by:
131 Wilf. (G.Wilford@ee.surrey.ac.uk).
133 Fabrizio Polacco (fpolacco@debian.org).
134 Colin Watson (cjwatson@debian.org).
135 Colin Watson wrote the current incarnation of the command-line front-
137 end, as well as this man page.
138
140 https://gitlab.com/man-db/man-db/-/issues
141 https://savannah.nongnu.org/bugs/?group=man-db
1422.11.2 2023-01-08 LEXGROG(1)