GLIMPSE(l)

NAME
glimpse 4.1 - search quickly through entire file systems

OVERVIEW
Glimpse (which stands for GLobal IMPlicit SEarch) is a very popular UNIX indexing and query system that allows you to search through a large set of files very quickly. Glimpse supports most of agrep's options (agrep is our powerful version of grep) including approximate matching (e.g., finding misspelled words), Boolean queries, and even some limited forms of regular expressions. It is used in the same way, except that you don't have to specify file names. So, if you are looking for a needle anywhere in your file system, all you have to do is say glimpse needle and all lines containing needle will appear preceded by the file name.

To use glimpse you first need to index your files with glimpseindex. For example, glimpseindex -o ~ will index everything at or below your home directory. See man glimpseindex for more details.

Glimpse is also available for web sites, as a set of tools called WebGlimpse. (The old glimpseHTTP is no longer supported and is not recommended.) See http://webglimpse.net/ for more information.

Glimpse includes all of agrep and can be used instead of agrep by giving a file name(s) at the end of the command. This will cause glimpse to ignore the index and run agrep as usual. For example, glimpse -1 pattern file is the same as agrep -1 pattern file. Agrep is distributed as a self-contained package within glimpse, and can be used separately. We added a new option to agrep: -r searches recursively the directory and everything below it (see agrep options below); it is used only when glimpse reverts to agrep.

Mail majordomo@webglimpse.net with SUBSCRIBE wgusers in the body to be added to the Webglimpse users mailing list. This is now the location where glimpse questions are also discussed. Bugs can be reported at http://webglimpse.net/bugzilla/ HTML version of these manual pages can be found in http://webglimpse.net/docs/glimpsehelp.html Also, see the glimpse home pages in http://webglimpse.net/glimpse

SYNOPSIS
glimpse - [almost all letters] pattern

INTRODUCTION
We start with simple ways to use glimpse and describe all the options in detail later on. Once an index is built, using glimpseindex, searching for pattern is as easy as saying

glimpse pattern

The output of glimpse is similar to that of agrep (or any other grep). The pattern can be any agrep legal pattern including a regular expression or a Boolean query (e.g., searching for Tucson AND Arizona is done by glimpse 'Tucson;Arizona').

The speed of glimpse depends mainly on the number and sizes of the files that contain a match and only to a second degree on the total size of all indexed files. If the pattern is reasonably uncommon, then all matches will be reported in a few seconds even if the indexed files total 500MB or more. Some information on how glimpse works and a reference to a detailed article are given below.

Most of agrep (and other grep's) options are supported, including approximate matching. For example,

glimpse -1 'Tuson;Arezona'

will output all lines containing both patterns allowing one spelling error in any of the patterns (either insertion, deletion, or substitution), which in this case is definitely needed.

glimpse -w -i 'parent'

specifies case insensitive (-i) and match on complete words (-w). So 'Parent' and 'PARENT' will match, 'parent/child' will match, but 'parenthesis' or 'parents' will not match. (Starting at version 3.0, glimpse can be much faster when these two options are specified, especially for very large indexes. You may want to set an alias especially for "glimpse -w -i".)

The -F option provides a pattern that must match the file name. For example,

glimpse -F '\.c$' needle

will find the pattern needle in all files whose name ends with .c. (Glimpse will first check its index to determine which files may contain the pattern and then run agrep on the file names to further limit the search.) The -F option should not be put at the end after the main pattern (e.g., "glimpse needle -F hay" is incorrect).

A Detailed Description of All the Options of Glimpse

-#  # is an integer between 1 and 8 specifying the maximum number of errors permitted in finding the approximate matches (the default is zero). Generally, each insertion, deletion, or substitution counts as one error. It is possible to adjust the relative cost of insertions, deletions and substitutions (see -I -D and -S options). Since the index stores only lower case characters, errors of substituting upper case with lower case may be missed (see LIMITATIONS). Allowing errors in the match requires more time and can slow down the match by a factor of 2-4. Be very careful when specifying more than one error, as the number of matches tend to grow very quickly.

-a  prints attribute names. This option applies only to Harvest SOIF structured data (used with glimpseindex -s). (See http://harvest.sourceforge.net/ for more information about the Harvest project.)

-A  used for glimpse internals.

-b  prints the byte offset (from the beginning of the file) of the end of each match. The first character in a file has offset 0.

-B  Best match mode. (Warning: -B sometimes misses matches. It is safer to specify the number of errors explicitly.) When -B is specified and no exact matches are found, glimpse will continue to search until the closest matches (i.e., the ones with minimum number of errors) are found, at which point the following message will be shown: "the best match contains x errors, there are y matches, output them? (y/n)" This message refers to the number of matches found in the index. There may be many more matches in the actual text (or there may be none if -F is used to filter files). When the -#, -c, or -l options are specified, the -B option is ignored. In general, -B may be slower than -#, but not by very much. Since the index stores only lower case characters, errors of substituting upper case with lower case may be missed (see LIMITATIONS).

-c  Display only the count of matching records. Only files with count > 0 are displayed.

-C  tells glimpse to send its queries to glimpseserver.

-d 'delim'
    Define delim to be the separator between two records. The default value is '$', namely a record is by default a line. delim can be a string of size at most 8 (with possible use of ^ and $), but not a regular expression. Text between two delim's, before the first delim, and after the last delim is considered as one record. For example, -d '$$' defines paragraphs as records and -d '^From ' defines mail messages as records. glimpse matches each record separately. This option does not currently work with regular expressions. The -d option is especially useful for Boolean AND queries, because the patterns need not appear in the same line but in the same record. For example, glimpse -F mail -d '^From ' 'glimpse;arizona;announcement' will output all mail messages (in their entirety) that have the 3 patterns anywhere in the message (or the header), assuming that files with 'mail' in their name contain mail messages. If you want the scope of the record to be the whole file, use the -W option. Glimpse warning: Use this option with care. If the delimiter is set to match mail messages, for example, and glimpse finds the pattern in a regular file, it may not find the delimiter and will therefore output the whole file. (The -t option - see below - can be used to put the delim at the end of the record.) Performance Note: Agrep (and glimpse) resorts to more complex search when the -d option is used. The search is slower and unfortunately no more than 32 characters can be used in the pattern.

-Dk Set the cost of a deletion to k (k is a positive integer). This option does not currently work with regular expressions.

-e pattern
    Same as a simple pattern argument, but useful when the pattern begins with a `-'.

-E  prints the lines in the index (as they appear in the index) which match the pattern. Used mostly for debugging and maintenance of the index. This is not an option that a user needs to know about.

-f file_name
    this option has a different meaning for agrep than for glimpse: In glimpse, only the files whose names are listed in file_name are matched. (The file names have to appear as in .glimpse_filenames.) In agrep, the file_name contains the list of the patterns that are searched. (Starting at version 3.6, this option for glimpse is much faster for large files.)

-F file_pattern
    limits the search to those files whose name (including the whole path) matches file_pattern. This option can be used in a variety of applications to provide limited search even for one large index. If file_pattern matches a directory, then all files with this directory on their path will be considered. To limit the search to actual file names, use $ at the end of the pattern. file_pattern can be a regular expression and even a Boolean pattern. This option is implemented by running agrep file_pattern on the list of file names obtained from the index. Therefore, searching the index itself takes the same amount of time, but limiting the second phase of the search to only a few files can speed up the search significantly. For example,

    glimpse -F 'src#\.c$' needle

    will search for needle in all .c files with src somewhere along the path. The -F file_pattern must appear before the search pattern (e.g., glimpse needle -F '\.c$' will not work). It is possible to use some of agrep's options when matching file names. In this case all options as well as the file_pattern should be in quotes. (-B and -v do not work very well as part of a file_pattern.) For example,

    glimpse -F '-1 \.html' pattern

    will allow one spelling error when matching .html to the file names (so ".htm" and ".shtml" will match as well).

    glimpse -F '-v \.c$' counter

    will search for 'counter' in all files except for .c files.

-g  prints the file number (its position in the .glimpse_filenames file) rather than its name.

-G  Output the (whole) files that contain a match.

-h  Do not display filenames.

-H directory_name
    searches for the index and the other .glimpse files in directory_name. The default is the home directory. This option is useful, for example, if several different indexes are maintained for different archives (e.g., one for mail messages, one for source code, one for articles).

-i  Case-insensitive search — e.g., "A" and "a" are considered equivalent. Glimpse's index stores all patterns in lower case (see LIMITATIONS below). Performance Note: When -i is used together with the -w option, the search may become much faster. It is recommended to have -i and -w as defaults, for example, through an alias. We use the following alias in our .cshrc file
    alias glwi 'glimpse -w -i'

-Ik Set the cost of an insertion to k (k is a positive integer). This option does not currently work with regular expressions.

-j  If the index was constructed with the -t option, then -j will output the files last modification dates in addition to everything else. There are no major performance penalties for this option.

-J host_name
    used in conjunction with glimpseserver (-C) to connect to one particular server.

-k  No symbol in the pattern is treated as a meta character. For example, glimpse -k 'a(b|c)*d' will find the occurrences of a(b|c)*d whereas glimpse 'a(b|c)*d' will find substrings that match the regular expression 'a(b|c)*d'. (The only exception is ^ at the beginning of the pattern and $ at the end of the pattern, which are still interpreted in the usual way. Use \^ or \$ if you need them verbatim.)

-K port_number
    used in conjunction with glimpseserver (-C) to connect to one particular server at the specified TCP port number.

-l  Output only the files names that contain a match. This option differs from the -N option in that the files themselves are searched, but the matching lines are not shown.

-L x | x:y | x:y:z
    if one number is given, it is a limit on the total number of matches. Glimpse outputs only the first x matches. If -l is used (i.e., only file names are sought), then the limit is on the number of files; otherwise, the limit is on the number of records. If two numbers are given (x:y), then y is an added limit on the total number of files. If three numbers are given (x:y:z), then z is an added limit on the number of matches per file. If any of the x, y, or z is set to 0, it means to ignore it (in other words 0 = infinity in this case); for example, -L 0:10 will output all matches to the first 10 files that contain a match. This option is particularly useful for servers that needs to limit the amount of output provided to clients.

-m  used for glimpse internals.

-M  used for glimpse internals.

-n  Each matching record (line) is prefixed by its record (line) number in the file. Performance Note: To compute the record/line number, agrep needs to search for all record delimiters (or line breaks), which can slow down the search.

-N  searches only the index (so the search is faster). If -o or -b are used then the result is the number of files that have a potential match plus a prompt to ask if you want to see the file names. (If -y is used, then there is no prompt and the names of the files will be shown.) This could be a way to get the matching file names without even having access to the files themselves. However, because only the index is searched, some potential matches may not be real matches. In other words, with -N you will not miss any file but you may get extra files. For example, since the index stores everything in lower case, a case-sensitive query may match a file that has only a case-insensitive match. Boolean queries may match a file that has all the keywords but not in the same line (indexing with -b allows glimpse to figure out whether the keywords are close, but it cannot figure out from the index whether they are exactly on the same line or in the same record without looking at the file). If the index was not build with -o or -b, then this option outputs the number of blocks matching the pattern. This is useful as an indication of how long the search will take. All files are partitioned into usually 200-250 blocks. The file .glimpse_statistics contains the total number of blocks (or glimpse -N a will give a pretty good estimate; only blocks with no occurrences of 'a' will be missed).

-o  the opposite of -t: the delimiter is not output at the tail, but at the beginning of the matched record.

-O  the file names are not printed before every matched record; instead, each filename is printed just once, and all the matched records within it are printed after it.

-p  (from version 4.0B1 only) Supports reading compressed set of filenames. The -p option allows you to utilize compressed `neighborhoods' (sets of filenames) to limit your search, without uncompressing them. Added mostly for WebGlimpse. The usage is:
    "-p filename:X:Y:Z" where "filename" is the file with compressed neighborhoods, X is an offset into that file (usually 0, must be a multiple of sizeof(int)), Y is the length glimpse must access from that file (if 0, then whole file; must be a multiple of sizeof(int)), and Z must be 2 (it indicates that "filename" has the sparse-set representation of compressed neighborhoods: the other values are for internal use only). Note that any colon ":" in filename must be escaped using a backslash .

-P  used for glimpse internals.

-q  prints the offsets of the beginning and end of each matched record. The difference between -q and -b is that -b prints the offsets of the actual matched string, while -q prints the offsets of the whole record where the match occurred. The output format is @x{y}, where x is the beginning offset and y is the end offset.

-Q  when used together with -N glimpse not only displays the filename where the match occurs, but the exact occurrences (offsets) as seen in the index. This option is relevant only if the index was built with -b; otherwise, the offsets are not available in the index. This option is ignored when used not with -N.

-r  This option is an agrep option and it will be ignored in glimpse, unless glimpse is used with a file name at the end which makes it run as agrep. If the file name is a directory name, the -r option will search (recursively) the whole directory and everything below it. (The glimpse index will not be used.)

-R k
    defines the maximum size (in bytes) of a record. The maximum value (which is the default) is 48K. Defining the maximum to be lower than the deafult may speed up some searches.

-s  Work silently, that is, display nothing except error messages. This is useful for checking the error status.

-Sk Set the cost of a substitution to k (k is a positive integer). This option does not currently work with regular expressions.

-t  Similar to the -d option, except that the delimiter is assumed to appear at the end of the record. Glimpse will output the record starting from the end of delim to (and including) the next delim. (See warning for the -d option.)

-T directory
    Use directory as a place where temporary files are built. (Glimpse produces some small temporary files usually in /tmp.) This option is useful mainly in the context of structured queries for the Harvest project, where the temporary files may be non-trivial, and the /tmp directory may not have enough space for them.

-U  (starting at version 4.0B1) Interprets an index created with the -X or the -U option in glimpseindex. Useful mostly for WebGlimpse or similar web applications. When glimpse outputs matches, it will display the filename, the URL, and the title automatically.

-v  (This option is an agrep option and it will be ignored in glimpse, unless glimpse is used with a file name at the end which makes it run as agrep.) Output all records/lines that do not contain a match. (Glimpse does not support the NOT operator yet.)

-V  prints the current version of glimpse.

-w  Search for the pattern as a word — i.e., surrounded by non-alphanumeric characters. For example, glimpse -w car will match car, but not characters and not car10. The non-alphanumeric must surround the match; they cannot be counted as errors. This option does not work with regular expressions. Performance Note: When -w is used together with the -i option, the search may become much faster. The -w will not work with $, ^, and _ (see BUGS below). It is recommended to have -i and -w as defaults, for example, through an alias. We use the following alias in our .cshrc file
    alias glwi 'glimpse -w -i'

-W  The default for Boolean AND queries is that they cover one record (the default for a record is one line) at a time. For example, glimpse 'good;bad' will output all lines containing both 'good' and 'bad'. The -W option changes the scope of Booleans to be the whole file. Within a file glimpse will output all matches to any of the patterns. So, glimpse -W 'good;bad' will output all lines containing 'good' or 'bad', but only in files that contain both patterns. The NOT operator '~' can be used only with -W. It is described later on. The OR operator is essentially unaffected (unless it is in combination with the other Boolean operations). For structured queries, the scope is always the whole attribute or file.

-x  The pattern must match the whole line. (This option is translated to -w when the index is searched and it is used only when the actual text is searched. It is of limited use in glimpse.)

-X  (from version 4.0B1 only) Output the names of files that contain a match even if these files have been deleted since the index was built. Without this option glimpse will simply ignore these files.

-y  Do not prompt. Proceed with the match as if the answer to any prompt is y. Servers (or any other scripts) using glimpse will probably want to use this option.

-Y k
    If the index was constructed with the -t option, then -Y x will output only matches to files that were created or modified within the last x days. There are no major performance penalties for this option.

-z  Allow customizable filtering, using the file .glimpse_filters to perform the programs listed there for each match. The best example is compress/decompress. If .glimpse_filters include the line
    *.Z uncompress <
    (separated by tabs) then before indexing any file that matches the pattern "*.Z" (same syntax as the one for .glimpse_exclude) the command listed is executed first (assuming input is from stdin, which is why uncompress needs <) and its output (assuming it goes to stdout) is indexed. The file itself is not changed (i.e., it stays compressed). Then if glimpse -z is used, the same program is used on these files on the fly. Any program can be used (we run 'exec'). For example, one can filter out parts of files that should not be indexed. Glimpseindex tries to apply all filters in .glimpse_filters in the order they are given. For example, if you want to uncompress a file and then extract some part of it, put the compression command (the example above) first and then another line that specifies the extraction. Note that this can slow down the search because the filters need to be run before files are searched. (See also glimpseindex.)

-Z  No op. (It's useful for glimpse's internals. Trust us.)

The characters `$', `^', `*', `[', `]', `^', `|', `(', `)', `!', and `\' can cause unexpected results when included in the pattern, as these characters are also meaningful to the shell. To avoid these problems, enclose the entire pattern in single quotes, i.e., 'pattern'. Do not use double quotes (").

PATTERNS

glimpse supports a large variety of patterns, including simple strings, strings with classes of characters, sets of strings, wild cards, and regular expressions (see LIMITATIONS).

Strings
    Strings are any sequence of characters, including the special symbols `^' for beginning of line and `$' for end of line. The following special characters ( `$', `^', `*', `[', `^', `|', `(', `)', `!', and `\' ) as well as the following meta characters special to glimpse (and agrep): `;', `,', `#', `<', `>', `-', and `.', should be preceded by `\' if they are to be matched as regular characters. For example, \^abc\\ corresponds to the string ^abc\, whereas ^abc corresponds to the string abc at the beginning of a line.

Classes of characters
    a list of characters inside [] (in order) corresponds to any character from the list. For example, [a-ho-z] is any character between a and h or between o and z. The symbol `^' inside [] complements the list. For example, [^i-n] denote any character in the character set except character 'i' to 'n'. The symbol `^' thus has two meanings, but this is consistent with egrep. The symbol `.' (don't care) stands for any symbol (except for the newline symbol).

Boolean operations
    Glimpse supports an `AND' operation denoted by the symbol `;' an `OR' operation denoted by the symbol `,', a limited version of a 'NOT' operation (starting at version 4.0B1) denoted by the symbol `~', or any combination. For example, glimpse 'pizza;cheeseburger' will output all lines containing both patterns. glimpse -F 'gnu;\.c$' 'define;DEFAULT' will output all lines containing both 'define' and 'DEFAULT' (anywhere in the line, not necessarily in order) in files whose name contains 'gnu' and ends with .c. glimpse '{political,computer};science' will match 'political science' or 'science of computers'. The NOT operation works only together with the -W option and it is generally applies only to the whole file rather to individual records. Its output may sometimes seem counterintuitive. Use with care. glimpse -W 'fame;~glory' will output all lines containing 'fame' in all files that contain 'fame' but do not contain 'glory'; This is the most common use of NOT, and in this case it works as expected. glimpse -W '~{fame;glory}' will be limited to files that do not contain both words, and will output all lines containing one of them.

Wild cards
    The symbol '#' is used to denote a sequence of any number (including 0) of arbitrary characters (see LIMITATIONS). 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 #.)

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
    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, glimpse '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. (If you use glimpse -w 'abc.*xyz', then 'abcxyz' will not be found, because glimpse will think that abc and xyz need to be matches to whole words.) 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). Some options (-d, -w, -t, -x, -D, -I, -S) do not currently work with regular expressions. The maximal number of errors for regular expressions that use '*' or '|' is 4. (See LIMITATIONS.)

structured queries
    Glimpse supports some form of structured queries using Harvest's SOIF format. See STRUCTURED QUERIES below for details.

EXAMPLES

(Run "glimpse '^glimpse' this-file" to get a list of all examples, some of which were given earlier.)

glimpse -F 'haystack.h$' needle
    finds all needles in all haystack.h's files.

glimpse -2 -F html Anestesiology
    outputs all occurrences of Anestesiology with two errors in files with html somewhere in their full name.

glimpse -l -F '\.c$' variablename
    lists the names of all .c files that contain variablename (the -l option lists file names rather than output the matched lines).

glimpse -F 'mail;1993' 'windsurfing;Arizona'
    finds all lines containing windsurfing and Arizona in all files having `mail' and '1993' somewhere in their full name.

glimpse -F mail 't.j@#uk'
    finds all mail addresses (search only files with mail somewhere in their name) from the uk, where the login name ends with t.j, where the . stands for any one character. (This is very useful to find a login name of someone whose middle name you don't know.)

glimpse -F mbox -h -G  . > MBOX
    concatenates all files whose name matches `mbox' into one big one.

SEARCHING IN COMPRESSED FILES

Glimpse includes an optional new compression program, called cast, which allows glimpse (and agrep) to search the compressed files without having to decompress them. The search is actually significantly faster when the files are compressed. However, we have not tested cast as thoroughly as we would have liked, and a mishap in a compression algorithm can cause loss of data, so we recommend at this point to use cast very carefully. We do not support or maintain cast. (Unless you specifically use cast, the default is to ignore it.)

GLIMPSEINDEX FILES

All files used by glimpse are located at the directory(ies) where the index(es) is (are) stored and have .glimpse_ as a prefix. The first two files (.glimpse_exclude and .glimpse_include) are optionally supplied by the user. The other files are built and read by glimpse.

.glimpse_exclude
    contains a list of files that glimpseindex is explicitly told to ignore. In general, the syntax of .glimpse_exclude/include is the same as that of agrep (or any other grep). The lines in the .glimpse_exclude file are matched to the file names, and if they match, the files are excluded. Notice that agrep matches to parts of the string! e.g., agrep /ftp/pub will match /home/ftp/pub and /ftp/pub/whatever. So, if you want to exclude /ftp/pub/core, you just list it, as is, in the .glimpse_exclude file. If you put "/home/ftp/pub/cdrom" in .glimpse_exclude, every file name that matches that string will be excluded, meaning all files below it. You can use ^ to indicate the beginning of a file name, and $ to indicate the end of one, and you can use * and ? in the usual way. For example /ftp/*html will exclude /ftp/pub/foo.html, but will also exclude /home/ftp/pub/html/whatever; if you want to exclude files that start with /ftp and end with html use ^/ftp*html$ Notice that putting a * at the beginning or at the end is redundant (in fact, in this case glimpseindex will remove the * when it does the indexing). No other meta characters are allowed in .glimpse_exclude (e.g., don't use .* or # or |). Lines with * or ? must have no more than 30 characters. Notice that, although the index itself will not be indexed, the list of file names (.glimpse_filenames) will be indexed unless it is explicitly listed in .glimpse_exclude.

.glimpse_filters
    See the description above for the -z option.

.glimpse_include
    contains a list of files that glimpseindex is explicitly told to include in the index even though they may look like non-text files. Symbolic links are followed by glimpseindex only if they are specifically included here. If a file is in both .glimpse_exclude and .glimpse_include it will be excluded.

.glimpse_filenames
    contains the list of all indexed file names, one per line. This is an ASCII file that can also be used with agrep to search for a file name leading to a fast find command. For example,
    glimpse 'count#\.c$' ~/.glimpse_filenames
    will output the names of all (indexed) .c files that have 'count' in their name (including anywhere on the path from the index). Setting the following alias in the .login file may be useful:
    alias findfile 'glimpse -h :1 ~/.glimpse_filenames'

.glimpse_index
    contains the index. The index consists of lines, each starting with a word followed by a list of block numbers (unless the -o or -b options are used, in which case each word is followed by an offset into the file .glimpse_partitions where all pointers are kept). The block/file numbers are stored in binary form, so this is not an ASCII file.

.glimpse_messages
    contains the output of the -w option (see above).

.glimpse_partitions
    contains the partition of the indexed space into blocks and, when the index is built with the -o or -b options, some part of the index. This file is used internally by glimpse and it is a non-ASCII file.

.glimpse_statistics
    contains some statistics about the makeup of the index. Useful for some advanced applications and customization of glimpse.

.glimpse_turbo
    An added data structure (used under glimpseindex -o or -b only) that helps to speed up queries significantly for large indexes. Its size is 0.25MB. Glimpse will work without it if needed.

STRUCTURED QUERIES
Glimpse can search for Boolean combinations of "attribute=value" terms by using the Harvest SOIF parser library (in glimpse/libtemplate). To search this way, the index must be made by using the -s option of glimpseindex (this can be used in conjunction with other glimpseindex options). For glimpse and glimpseindex to recognize "structured" files, they must be in SOIF format. In this format, each value is prefixed by an attribute-name with the size of the value (in bytes) present in "{}" after the name of the attribute. For example, The following lines are part of an SOIF file:
type{17}:       Directory-Listing
md5{32}:        3858c73d68616df0ed58a44d306b12ba
Any string can serve as an attribute name. Glimpse "pattern;type=Directory-Listing" will search for "pattern" only in files whose type is "Directory-Listing". The file itself is considered to be one "object" and its name/url appears as the first attribute with an "@" prefix; e.g., @FILE { http://xxx... } The scope of Boolean operations changes from records (lines) to whole files when structured queries are used in glimpse (since individual query terms can look at different attributes and they may not be "covered" by the record/line). Note that glimpse can only search for patterns in the value parts of the SOIF file: there are some attributes (like the TTL, MD5, etc.) that are interpreted by Harvest's internal routines. See RFC 2655 for more detailed information of the SOIF format.

REFERENCES

1.  U. Manber and S. Wu, "GLIMPSE: A Tool to Search Through Entire File Systems," Usenix Winter 1994 Technical Conference (best paper award), San Francisco (January 1994), pp. 23-32. Also, Technical Report #TR 93-34, Dept. of Computer Science, University of Arizona, October 1993 (a postscript file is available by anonymous ftp at ftp://webglimpse.net/pub/glimpse/TR93-34.ps).

2.  S. Wu and U. Manber, "Fast Text Searching Allowing Errors," Communications of the ACM 35 (October 1992), pp. 83-91.

SEE ALSO
agrep(1), ed(1), ex(1), glimpseindex(1), glimpseserver(1), grep(1), sh(1), csh(1).

LIMITATIONS

The index of glimpse is word based. A pattern that contains more than one word cannot be found in the index. The way glimpse overcomes this weakness is by splitting any multi-word pattern into its set of words and looking for all of them in the index. For example, glimpse 'linear programming' will first consult the index to find all files containing both linear and programming, and then apply agrep to find the combined pattern. This is usually an effective solution, but it can be slow for cases where both words are very common, but their combination is not.

As was mentioned in the section on PATTERNS above, some characters serve as meta characters for glimpse and need to be preceded by '\' to search for them. The most common examples are the characters '.' (which stands for a wild card), and '*' (the Kleene closure). So, "glimpse ab.de" will match abcde, but "glimpse ab\.de" will not, and "glimpse ab*de" will not match ab*de, but "glimpse ab\*de" will. The meta character - is translated automatically to a hypen unless it appears between [] (in which case it denotes a range of characters).

The index of glimpse stores all patterns in lower case. When glimpse searches the index it first converts all patterns to lower case, finds the appropriate files, and then searches the actual files using the original patterns. So, for example, glimpse ABCXYZ will first find all files containing abcxyz in any combination of lower and upper cases, and then searches these files directly, so only the right cases will be found. One problem with this approach is discovering misspellings that are caused by wrong cases. For example, glimpse -B abcXYZ will first search the index for the best match to abcxyz (because the pattern is converted to lower case); it will find that there are matches with no errors, and will go to those files to search them directly, this time with the original upper cases. If the closest match is, say AbcXYZ, glimpse may miss it, because it doesn't expect an error. Another problem is speed. If you search for "ATT", it will look at the index for "att". Unless you use -w to match the whole word, glimpse may have to search all files containing, for example, "Seattle" which has "att" in it.

There is no size limit for simple patterns and simple patterns within Boolean expressions. More complicated patterns, such as regular expressions, are currently limited to approximately 30 characters. Lines are limited to 1024 characters. Records are limited to 48K, and may be truncated if they are larger than that. The limit of record length can be changed by modifying the parameter Max_record in agrep.h.

Glimpseindex does not index words of size > 64.

BUGS

In some rare cases, regular expressions using * or # may not match correctly.

A query that contains no alphanumeric characters is not recommended (unless glimpse is used as agrep and the file names are provided). This is an understatement.

The notion of "match to the whole word" (the -w option) can be tricky sometimes. For example, glimpse -w 'word$' will not match 'word' appearing at the end of a line, because the extra '$' makes the pattern more than just one simple word. The same thing can happen with ^ and with _. To be on the safe side, use the -w option only when the patterns are actual words.

Please send bug reports or comments to gvelez@webglimpse.net.

DIAGNOSTICS
Exit status is 0 if any matches are found, 1 if none, 2 for syntax errors or inaccessible files.

AUTHORS
Udi Manber and Burra Gopal, Department of Computer Science, University of Arizona, and Sun Wu, the National Chung-Cheng University, Taiwan. Now maintained by Golda Velez at Internet WorkShop (Email: gvelez@webglimpse.net)