Extracted from the Glimpse Man Page
The font size is increased here so you can read the commas, quotes, and
semi colins.
Boolean operations
Wild cards
Combination of exact and approximate matching
Any pattern inside angle brackets <> must match
the text exactly even if the match is with errors.
For example, <mathemat>ics matches mathematical
with one error (replacing the last s with an a), but
mathe<matics> does not match mathematical no
matter how many errors are allowed. (This option is
buggy at the moment.)
Regular expressions
Glimpse (the search engine) supports an `AND' operation denoted
by the symbol `;' an `OR' operation denoted by the
symbol `,', or any combination. For example, `pizza;cheeseburger' will output all
lines containing both patterns. define;DEFAULT'
will output all lines containing both `define' and
`DEFAULT' (anywhere in the line, not necessarily in
order). `{political,computer};science'
will match `political science' or `science of computers'.
The symbol `#' is used to denote a sequence of any
number (including 0) of arbitrary characters.
The symbol # is equivalent to .* in egrep. In fact,
.* will work too, because it is a valid regular expression
(see below), but unless this is part of an actual regular
expression, # will work faster. (Currently glimpse
is experiencing some problems with #.)
Since the index is word based, a regular expression
must match words that appear in the index for glimpse
to find it. Glimpse first strips the regular expression
from all non-alphabetic characters, and searches the
index for all remaining words. It then applies the
regular expression matching algorithm to the files
found in the index. For example, `abc.*xyz'
will search the index for all files that contain both
`abc' and `xyz', and then search directly for `abc.*xyz'
in those files. The syntax of regular expressions in glimpse
is in general the same as that for agrep. The
union operation `|', Kleene closure `*', and parentheses
() are all supported. Currently `+' is not supported.
Regular expressions are currently limited to approximately
30 characters (generally excluding meta characters). The maximal number of
errors for regular expressions that use `*' or `|'
is 4.