@node Apropos, Arithmetic, Angle, Commands

@iftex
@syntax Apropos.
@end iftex
@example
Syntax: APROPOS pattern
@end example
@pindex Apropos

@findex help (see also apropos)

   Apropos lists all macros whose name or introductory comments match
the given pattern. Probably the most common use for the command is
simply to look for a word -- e.g. @code{APROPOS histogram}.

   If your system supports it, APROPOS will also search the help files
for the given pattern (in this case matches may not extend over more
than one line). If @code{VERBOSE} is zero only the line containing the
match is printed; if @code{VERBOSE} is one or more then a couple of
lines on each side of the match are printed too.  If the pattern
matches more than once each match will be printed, merged together if
appropriate and separated by line of dashes otherwise.  If you use `q'
to stop looking at the help files APROPOS will immediately proceed to
search the macros.

The pattern is a slightly restricted version of a
normal Unix regular expression, specifically:
@table @code
@item .
Matches any character except \n.
@item [...]
Matches any of the characters listed in the @code{[ ]}.

If the first character is a ^ it means use anything except
the range specified (in any other position ^ isn't special)

A range may be specified with a - (e.g. [0-9]), and if a ]
is to be part of the range, it must appear first (or after
the leading ^, if specified). A - may appear as
the special range @code{---}.

@item ^
Matches only at the start of the string. Note that you must quote
the @code{^} with an @key{ESQ-q} if you use it as your history
character -- look in the index under @code{history} to learn how
to change it.

@item $
Matches only at the end of a string.

@item \t
Tab

@item \n
Newline

@item \.
(any other character) simply escapes the character (e.g. \^)

@item *
Any number of the preceding character (or range)

@item ?
One or more of the preceding character or range
@end table

By default searches are case insensitive, but you can make searching
sensitive to case by deleting the variable case_fold_search (you can do this
by putting a line @code{case_fold_search 0} in your @file{.sm} file if you
so desire).

The name and the comments are searched separately, so you could list
all macros beginning with a, b, c, d, e, or z by saying
@example
APROPOS ^[a-ez]
@end example
@noindent
(which works because all comments start with a @code{#}),
or
@example
APROPOS "^#[^#]"
@end example
@noindent
to list all macros that start with a single @code{#} (the quotes are
needed to stop the @code{#}'s from being treated as comment characters).