     [file version.texi not included]

     START-INFO-DIR-ENTRY
     * ID database: (id-utils).              Identifier database utilities.
     * mkid: (id-utils)mkid invocation.      Creating an ID database.
     * lid: (id-utils)lid invocation.        Matching words and patterns.
     * fid: (id-utils)fid invocation.        Listing a file's tokens.
     * fnid: (id-utils)fnid invocation.      Looking up file names.
     * xtokid: (id-utils)xtokid invocation.  Testing mkid scanners.
     END-INFO-DIR-ENTRY

This file documents the id-utils database utilities.

Copyright (C) 1996 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation.

ID utilities
************

This manual documents version VERSION of the ID utilities.

Introduction
************

An ID database is a binary file containing a list of file names, a list of tokens, and a sparse matrix indicating which tokens appear in which files.

With this database and some tools to query it (described in this manual), many text-searching tasks become simpler and faster.  For example, you can list all files that reference a particular #include file throughout a huge source hierarchy, search for all the memos containing references to a project, or automatically invoke an editor on all files containing references to some function or variable. Anyone with a large software project to maintain, or a large set of text files to organize, can benefit from the ID utilities.

Although the name `ID' is short for `identifier', the ID utilities handle more than just identifiers; they also treat other kinds of tokens, most notably numeric constants, and the contents of certain character strings.  Thus, this manual will use the word token as a term that is inclusive of identifiers, numbers and strings.

There are several programs in the ID utilities family:

mkid
     scans files for tokens and builds the ID database file.

lid
     queries the ID database for tokens, then reports matching file names or matching lines.

fid
     lists all tokens recorded in the database for given files, or tokens common to two files.

fnid
     matches the file names in the database, rather than the tokens.

xtokid
     extracts raw tokens---helps with testing of new mkid scanners.

In addition, the ID utilities have historically provided several query programs which are specializations of lid:

gid
     (alias for lid -R grep) lists all lines containing the requested pattern.

eid
     (alias for lid -R edit) invokes an editor on all files containing the requested pattern, and if possible, initiates a text search for that pattern.

aid
     (alias for lid -ils) treats the requested pattern as a case-insensitive literal substring.

Please report bugs to bug-gnu-utils@gnu.ai.mit.edu.  Remember to include the version number, machine architecture, input files, and any other information needed to reproduce the bug: your input, what you expected, what you got, and why it is wrong.  Diffs are welcome, but please include a description of the problem as well, since this is sometimes difficult to infer.  See Bugs (GNU CC).

Quick Start Procedure
*********************

     Unpack the distribution.

     Type ./configure

     Type make

     Type make install as a user with the appropriate privileges (e.g., bin or perhaps even root).

     Type cd /usr/include; mkid to build an ID database covering all of the system header files.

     Type lid FILE, then gid strtok, then aid stdout.

You have just built, installed and used the most common commands of the GNU ID utilities.  If you ever need help remembering which system header files contain a particular declaration, or reference a particular symbol, you'll want to keep the ID file you built in /usr/include for later use.  If your working directory is elsewhere at the time, simply provide the -f /usr/include option to lid (see Reading options).

Common command-line options
***************************

Certain options, and regular expression syntax, are shared by various groupings of the ID utilities.  We describe these in the sections below, rather than repeating them for each program.

Options Common to All Programs
==============================

--help
     Print a usage message listing all available options, then exit successfully.

--version
     Print the version number, then exit successfully.

Options for Programs that Read ID Databases
===========================================

-f FILENAME
--file=FILENAME

     FILENAME is the ID database to read when processing queries.  At present, only a single --file option is processed, but in future releases, more than one ID database may be named on the command line.

$IDPATH

     IDPATH is an environment variable that contains a colon-separated list of ID database names.  If this variable is present, and no --file options are presented on the command line, the ID databases named in IDPATH are implied. (At present, this feature is fully implemented, since only the first of a list of ID database names is processed.)

If no ID databases are specified either on the command line or via the IDPATH environment variable, then the ID utilities search for a file named ID in the current working directory, and then in successive parent directories.

Options for Programs that Write ID Databases
============================================

-o FILENAME
--output=FILENAME

     The --output option names the file in which to write a new ID database.  If no --output (or --file) option is present, an output file named ID is implied.

-f FILENAME
--file=FILENAME

     This is a synonym for --output

Options for Programs that Walk File and Directory Trees.
========================================================

The programs mkid and xtokid accept the names of files and directories on the command line.  Files are scanned if there is a scanner available and enabled for the file's source language. Directories are recursively descended, searching for files whose names match the rules listed in the language map file (see Language map).

The following option controls the file tree walker:

-p NAMES
--prune=NAMES

     One or more file or directory names may appear in NAMES.  The file tree walker will stop short at these files and directories and their contents will not be scanned.

Options for Programs that List File Names
=========================================

The programs lid and fnid can print lists of file names as the result of queries.  The following option controls how these lists are formatted:

-S STYLE
--separator=STYLE

     STYLE may be one of braces, space or newline.

     The STYLE of braces means that file names with common directory prefix and common suffix are printed using the shell's brace notation in order to compress the output.  For example, ../src/foo.c ../src/bar.c can be printed in brace notation as ../src/{foo,bar}.c.

     The STYLEs of space and newline mean that file names are separated spaces or by newlines, respectively.

     If the list of files is being printed on a terminal, brace notation is the default.  If not, file names are separated by spaces if the KEY is included in the output, and by newlines the KEY STYLE is none (see lid invocation).

Options for Programs that Scan Source Files
===========================================

mkid and xtokid walk file trees, select source files by name, and extract tokens from source files.  They accept the following options:

-m MAPFILE
--lang-map=MAPFILE

     MAPFILE contains rules for determining the source languages from file names.  See Language map

-i LANGUAGES
--include=LANGUAGES

     The --include option names LANGUAGES whose source files should be scanned and incorporated into the ID database.  By default, all languages known to the ID utilities are enabled.

-x LANGUAGES
--exclude=LANGUAGES

     The --exclude option names LANGUAGES whose source files should NOT be scanned.  The default list of excluded languages is empty.  Note that only one of --include or --exclude may be specified on the command line for a single run.

-l LANGUAGE:OPTIONS
--lang-option=LANGUAGE:OPTIONS

     Language-specific scanners also accept options.  LANGUAGE denotes the desired scanner, and OPTION are the command-line options that should be passed through to it.  For example, to pass the -X --COKE-BOTTLE options to the scanner for the language SWIZZLE, pass this: -L SWIZZLE:"-X --COKE-BOTTLE", or this: -LANG-OPTION=SWIZZLE:"-X --COKE-BOTTLE", or this: -L SWIZZLE-X -L SWIZZLE:--COKE-BOTTLE.  Use the --help option to see the command-line option summary for

To determine which tokens to extract from a file and store in the database, mkid calls a scanner; we say a scanner recognizes a particular language.  Scanners for several languages are built-in to mkid; you can add your own scanners as well, as explained in Defining scanners.

The ID utilities determine which scanner to use for a particular file by consulting the language-map file.  Scanners for several are already built-in to the ID utilities.  You can see which languages have built-in scanners, and examine their language-specific options by invoking mkid --help or xtokid --help.

Mapping file names to source languages
--------------------------------------

The file id-lang.map, installed by default in $(prefix)/share/id-lang.map, contains rules for mapping file names to source languages.  Each rule comprises three parts: a shell GLOB pattern, a language name, and language-specific scanner options.

The special pattern ** denotes the default source language.  This is the language that's assigned to file names that don't match any other pattern.

The special pattern *** should be followed by a file name.  The named file should contain more language-map rules and is included at this point.

The order in which rules are presented in a language-map file is significant.  This order influences the order in which files are displayed as the result of queries.  For example, the distributed language-map file places all rules for C .H files ahead of .C files, so that in general, declarations will precede definitions in query output.  The same thing is done for C++ and its many different source file name extensions.

Here is a pared-down version of the id-lang.map file distributed with the ID utilities:

     # Default language
     **			IGNORE	# Although this is listed first,
     				# the default language pattern is
     				# logically matched last.

     # Backup files
     *~			IGNORE
     *.bak			IGNORE
     *.bk[0-9]		IGNORE

     # SCCS files
     [sp].*			IGNORE

     # list header files before code files
     *.h			C
     *.h.in			C
     *.H			C++
     *.hh			C++
     *.hpp			C++
     *.hxx			C++

     # list C `meta' files next
     *.l			C
     *.lex			C
     *.y			C
     *.yacc			C

     # list C code files after header files
     *.c			C
     *.C			C++
     *.cc			C++
     *.cpp			C++
     *.cxx			C++

     # list assembly language after C
     *.[sS]			asm --comment=;
     *.asm			asm --comment=;

     # [nt]roff
     *.[0-9]			roff
     *.ms			roff
     *.me			roff
     *.mm			roff

     # TeX and friends
     *.tex			TeX
     *.ltx			TeX
     *.texi			texinfo
     *.texinfo		texinfo

C/C++ Language Scanner
----------------------

The C scanner is the most commonly used.  Files that match the glob pattern *.h, *.c, as well as yacc files that match *.y or *.yacc, and lex files that match *.l or *.lex, are processed with this scanner.

Scanner-specific options (Note, these options are presented WITHOUT the required -l or --lang-option= prefix):

-k CHARACTER-CLASS
--keep=CHARACTER-CLASS

     Consider the characters in CHARACTER-CLASS as valid constituents of identifier names.  For example, if you are indexing C code that contains $ in some of its identifiers, you can include these by using --lang-option=C:--keep=$, or -l C:"-k $" (if you don't like to type so much).

-i CHARACTER-CLASS
--ignore=CHARACTER-CLASS

     x mkiConsider the characters in CHARACTER-CLASS as valid constituents of identifier names, but discard all tokens containing these characters. For example, if some C code has identifiers containing $, but you don't want these cluttering up your ID database, use --lang-option=C:--ignore=$, or the terser equivalent -l C:"-i $".

-u
--strip-underscore

     Strip one leading underscore from C identifiers encapsulated as character strings.  This option is useful if you are indexing C code that contains symbol-table name strings for systems that prepend an underscore to external symbols.  By default, the leading underscore is retained.

Assembly Language Scanner
-------------------------

Assembly languages use a variety of commenting conventions, and allow a variety of special characters to dirty up local symbols, preventing name space conflicts with symbols defined by higher-level languages.  Also, some compilation systems prepend an underscore to external symbols.  The options listed below are designed to address these differences.

-c CHARACTER-CLASS
--comment=CHARACTER-CLASS

     The characters in CHARACTER-CLASS are considered left delimiters for comments that extend until the end of the current line.

-k CHARACTER-CLASS
--keep=CHARACTER-CLASS

     Consider the characters of CHARACTER-CLASS as valid constituents of identifier names.  For example, if you are indexing assembly code that prepends . to assembler directives, and prepends % to register names, you can keep these characters in the tokens by specifying --lang-option=asm:--keep=.%, or -l asm:"-k .%".

-i CHARACTER-CLASS
--ignore=CHARACTER-CLASS

     Consider the characters of CHARACTER-CLASS as valid consituents of identifier names, but discard all tokens containing these characters. For example, if you don't want to clutter your ID database with assembler directives that begin with a leading . or with assembler labels that contain @, use --lang-option=asm:--ignore=.@, or -l asm:"-i .@".

-u
--strip-underscore

     Strip one leading underscore from identifiers.  This option is useful if your compilation system prepends an underscore to external symbols.  By stripping the underscore, you can canonicalize such names and bring them into conformance the way they are expressed in the C language.  By default, the leading underscore is retained.

-n
--no-cpp

     Do not recognize C preprocessor directives.  By default, such lines are handled in the same way as they are by the C language scanner.

Text Scanner
------------

The plain text scanner is intended for human-language documents, or as the scanner of last resort for files that have no scanner that is more specific.  It is customizable to the extent that character classes can be designated as token constituents or as token delimiters.  The default token constituents are the alpha-numerics; all other characters are considered token delimiters.

-i CHARACTER-CLASS
--include=CHARACTER-CLASS

     Include characters belonging to CHARACTER-CLASS in tokens.

-x CHARACTER-CLASS
--exclude=CHARACTER-CLASS

     Exclude characters belonging to CHARACTER-CLASS from tokens, i.e., treat them as token delimiters.

Defining New Scanners in the Source Code
----------------------------------------

To add a new scanner in source code, you should add a new section to the file scanners.c.  It might be easiest to clone one of the existing scanners and modify it as necessary.  For the hypothetical language FOO, you must define the functions get_token_foo, parse_args_foo, help_me_foo, as well as the tables long_options_foo and args_foo.  If your scanner is modelled after one of the existing scanners, you'll also need a character-attribute table ctype_foo.

This is not a terribly difficult programming task, but it requires recompiling and installing the new version of mkid and xtokid. You should use xtokid to test the operation of the new scanner.

Once these functions and tables are ready, add function prototypes and an entry to to the languages_0 table near the beginning of the file.

Be warned that the existing scanners are built for speed, not elegance or readability.  You might wish to create a new scanner that's easier to read and understand if you don't feel that speed is so important.

mkid: Creating an ID Database
*****************************

mkid builds an ID database.  It accepts the names of files and/or directories on the command line, selects files that have an enabled scanner, then extracts and stores tokens from those files.  The resulting ID database is architecture- and byte-order-independent so it can be shared among all systems.

The primary virtues of mkid are speed and high capacity.  The size of the source trees it can index is limited only by available system memory.  mkid's indexing algorithm is very space-efficient and exhibits excellent locality-of-reference, and so is capable of operating with a working-set size that is only half the size of its virtual address space.  A typical UNIX-like operating system with 16 megabytes of system memory should be able to build an ID database covering approximately 12,000-14,000 source files totalling approximately 50--100 Megabytes.  A 66 Mhz 486 computer can build such a large ID database in approximately 10-15 minutes.

In a future release, mkid will be able to incrementally update an ID database much faster than it can build one from scratch.  Until this feature becomes available, it might be a good idea to schedule a cron job to regularly update large ID databases during off-hours.

mkid writes the ID file, therefore it accepts the --output (and --file) options as described in Writing options. mkid extracts tokens from source files, therefore it accepts the --lang-map, --include, --exclude, and --lang-option options, as well as the language-specific scanner options, all of which are described in Extraction options. mkid walks file trees, therefore it handles file and directory names on its command line and the --prune option as described in Walker options.

In addition, mkid accepts the following command-line options:

-s
--statistics

     mkid reports statistics about resource usage at the end of its run.

-v
--verbose

     mkid reports statistics about each file as it is scanned, and about the resource usage of its indexing algorithm at regular intervals.

lid: Querying an ID Database by Token
*************************************

The lid program accepts PATTERNS on the command line which it matches against the tokens stored in an ID database.  The interpretation of a PATTERN is determined by the makeup of the PATTERN string itself, or can be overridden by command-line options.  If a PATTERN contains regular expression meta-characters, it is used to perform a regular-expression substring search.  If no such meta-characters are present, PATTERN is used to perform a literal word search.  (By default, all searches are sensitive to alphabetic case.)  If no PATTERN is supplied on the command line, lid lists every entry in the ID database.

lid reads the ID database, therefore it accepts the --file option, and consults the IDPATH environment variable, as described in Reading options.  lid lists file names, therefore it accepts the --separator option, as described in File listing options.

In addition, lid accepts the following command-line options:

-i
--ignore-case

     Ignoring differences in alphabetic case between the PATTERN and the tokens in the ID database.

-l
--literal

     Match PATTERN as a literal string.  Use this option if PATTERN contains regular-expression meta-characters, but you don't wish to perform a regular-expression search.

-r
--regexp

     Match PATTERN as an extended regular expression (Extended regular expressions are the same as those accepted by egrep.). Use this option if no regular-expression expression meta-characters are present in PATTERN, but you wish to force a regular-expression search (note: in this case, a literal substring search might be faster).

-w
--word

     Match PATTERN using a word-delimited (non substring) search.  This is the default for literal searches.

-s
--substring

     Match PATTERN using a substring (non word-delimited) search.  This is the default for regular expression searches.

-k STYLE
--key=STYLE

     STYLE can be one of token, pattern or none. This option controls how the subject of the query is presented.  This is best illustrated by example:

          $ lid --key=token '^dest.'
          destaddr       libsys/memcpy.c
          destination    libsys/regex.c
          destlst        libsys/rx.c
          destpos        libsys/rx.c
          destset        libsys/rx.h libsys/rx.c

          $ lid --key=pattern '^dest.'
          ^dest.         libsys/rx.h libsys/{memcpy,regex,rx}.c

          $ lid --key=none '^dest.'
          libsys/rx.h libsys/{memcpy,regex,rx}.c

     When --key is either token or pattern, the first column of output is a TOKEN or PATTERN, respectively.  When --key is none, neither of these is printed, and the file name list begins immediately.  The default is token.

-R STYLE
--result=STYLE

     STYLE can be one of filenames, grep, edit or none.  This option controls how the value associated with the query's KEY presented.  When STYLE is filenames, a list of file names is printed (this is the default).  When STYLE is grep, the lines that match PATTERN are printed in the same format as egrep -n.  When STYLE is edit, the file names are passed to an editor, and if possible PATTERN is passed as an initial search string (see eid invocation).  When STYLE is none, the file names are not processed in any way. This can be useful if you wish to see what tokens match a PATTERN, but don't care about where they reside.

-d
-o
-x

     These options may be used in any combination to specify the radix of numeric matches.  -d allows matching on decimal numbers, -o on octal numbers, and -x on hexadecimal numbers.  Any combination of these options may be used.  The default is to match all three radixes.

-F RANGE
--frequency=RANGE

     Match tokens whose occurrence count falls in RANGE.  RANGE may be expressed as a single number N, or as a range N..M.  Either limit of the range may be omitted (e.g., ..M, or N....).  If the lower limit N is omitted, it defaults to 1.  If the upper limit is omitted, it defaults in the present implementation to 65535, the maximum value of an unsigned 16-bit integer.

     Particularly useful queries are lid -F1, which helps locate identifiers that are defined but never used, or are used but never defined.  Similarly, lid -F2 can help find functions that possess a prototype declaration and a definition, but are never called.

-a NUMBER
--ambiguous=NUMBER

     List identifiers (not numbers) that are ambiguous for the first NUMBER characters.  This feature might be in useful when porting programs to ancient pea-brained compilers that don't support long identifier names.  However, the best long-term option is to set such systems on fire.

Aliases for Specialized lid Queries
===================================

Historically, the ID utilities have provided several query interfaces which are specializations of lid (see lid invocation).

gid
     (alias for lid -R grep) lists all lines containing the requested pattern.

eid
     (alias for lid -R edit) invokes an editor on all files containing the requested pattern, and optionally initiates a text search for that pattern.

aid
     (alias for lid -ils) treats the requested pattern as a case-insensitive literal substring.

GNU Emacs query interface
=========================

The id-utils source distribution comes with a file id-utils.el, which defines a GNU Emacs interface to gid.  To install it, put id-utils.el somewhere that Emacs will find it (i.e., in your load-path) and put

     (autoload 'gid "gid" nil t)

in one of Emacs' initialization files, e.g., ~/.emacs. You will then be able to use M-x gid to run the command.

The gid function prompts you with the word around point.  If you want to search for something else, simply delete the line and type the pattern of interest.

The function then runs the gid program in a *compilation* buffer, so the normal next-error function can be used to visit all the places the identifier is found (see Compilation (The GNU Emacs Manual)).

eid: Invoking an Editor on Query Results
========================================

lid -R edit is an editing interface for the ID utilities that is most commonly used with vi.  Emacs users should use the interface defined in id-utils.el (see Emacs gid interface).  The ID utilities include an alias called eid, and for the sake of brevity, we'll use this alias for the remainder of this section. eid performs a lid-style, then asks if you wish to edit the files.  If your query yields more than one line of output, you will be prompted after each line.  This is the prompt you'll see:

     Edit? [y1-9^S/nq]

You may respond with:

y
     Edit all files listed.

1...9
     Edit all files starting at the N + 1'st file.

/STRING or CTRL-SREGEXP
     Search into the file list, and begin editing with the first file name that matches the regular expression REGEXP.

n
     Don't edit any files.  If another line of query output is pending, advance to that line, for which another Edit? prompt will appear.

q
     Quit---don't edit any files, and don't process any more lines of query output.

Here is an example:

     prompt$ eid FILE \^print
     FILE           {ansi2knr,fid,filenames,idfile,idx,lid,misc,...}.c
     Edit? [y1-9^S/nq] n
     ^print         {ansi2knr,fid,getopt,getopt1,lid,mkid,regex,scanners}.c
     Edit? [y1-9^S/nq] 2

This will start editing at getopt.c.

eid invokes the editor defined by the environment variable VISUAL.  If VISUAL is undefined, it uses the environment variable EDITOR instead.  If EDITOR is undefined, it defaults to vi.  It is possible for eid to pass the editor an initial search pattern so that your cursor will immediately alight on the token of interest.  This feature is controlled by the following environment variables:

EIDARG
     A printf(3) format string for the editor argument to search for the matching token.  For vi, this should be +/%s/.

EIDLDEL
     The regular-expression meta-character(s) for delimiting the beginning of a word (the `eid Left DELimiter').  eid inserts this in front of the matching token when a word-search is desired.  For vi, this should be \<.

EIDRDEL
     The regular-expression meta-character(s) for delimiting the end of a word (the `eid Right DELimiter').  eid inserts this in end of the matching token when a word-search is desired.  For vi, this should be \>.

fid: Listing a file's tokens
****************************

fid prints the tokens found in a given file.  If two file names are passed on the command line, fid prints the tokens that are common to both files (i.e., the set intersection of the two token sets).

lid reads the ID database, therefore it accepts the --file option, and consults the IDPATH environment variable, as described in Reading options.

If the standard output is attached to a terminal, the printed tokens are separated by spaces.  Otherwise, the tokens are printed one per line.

fnid: Looking up filenames
**************************

fnid queries the list of file names stored in the ID database. It accepts shell wildcard patterns on the command line.  If no pattern is supplied, * is implied.  fnid prints the file names that match the given patterns.

fnid prints file names, and as such accepts the --separator option as described in File listing options.

For example, the command:

     fnid \*.c

lists all the .c files in the database.  (The \ here protects the * from being expanded by the shell.)

xtokid: Testing Language Scanners
*********************************

xtokid accepts the names of files and/or directories on the command line, then extracts and prints a stream of tokens from those files for which it has a valid, enabled scanner.  This is useful primarily for debugging new mkid scanners (see Defining scanners).

xtokid extracts tokens from source files, therefore it accepts the --lang-map, --include, --exclude, and --lang-option options, as well as the language-specific scanner options, all of which are described in Extraction options. xtokid walks file trees, therefore it handles file and directory names on its command line and the --prune option as described in Walker options.

The name xtokid indicates that it is the ``eXtract TOKens ID utility''.

Past and Future
***************

Greg McGary conceived of the ideas behind the ID utilities when he began working on the Unix kernel in 1984.  He needed a navigation tool to help him find his way around the expansive, unfamiliar landscape. The first id-utils-like tools were shell scripts, and produced an ASCII database that looks much like the output of lid ".*".  It took over an hour on a VAX 11/750 to build a database for a 4.1BSD derived kernel.  The first version of lid used the UNIX system utility look, modified to handle very long lines.

In 1986, Greg rewrote the shell scripts in C to improve performance. Build times for the ID file were shortened by an order of magnitude. The ID utilities were first posted to comp.sources.unix in September 1987 under the name id.

Over the next few years, several versions diverged from the original source.  Tom Horsley at Harris Computer Systems Division stepped forward to take over maintenance and integrated some of the fixes from divergent versions.  A first release of the renamed mkid version 2 was posted to alt.sources near the end of 1990.  At that time, Tom wrote a Texinfo manual with the encouragement the net community. (Tom especially thanks Doug Scofield and Bill Leonard whom he dragooned into helping poorfraed and edit---they found several problems in the initial version.)  Karl Berry revamped the manual for Texinfo style, indexing, and organization in 1995.

In January 1995, Greg McGary reemerged as the primary maintainer and launched development of mkid version 3, whose primary new feature is an efficient algorithm for building databases that is linear in both time and space over the size of the input text.  (The old algorithm was quadratic in space so it was incapable of handling very large source trees.)  For the first time, the code was released under the GNU Public License.

In June 1996, the package was renamed again to id-utils and was released for the first time under FSF copyright as part of the GNU system.  All programs had their command-line arguments completely revised.  The mkid and xtokid programs also gained a file-tree walker, so that directory names can be passed on the command line instead of the names of every individual file.  Greg reorganized and rewrote most of the Texinfo manual to reflect these changes.

Future releases of id-utils might include:

     an optional coupling with GNU grep, so that grep can use an ID database for hints

     a cscope work-alike query interface

     incremental update of the ID database.