     CTAGS(1)                      Darren Hiebert                       CTAGS(1)
     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

     NAME
          ctags - Generate tag files for source code

     SYNOPSIS
          ctags [options] [file(s)]

          etags [options] [file(s)]

     DESCRIPTION
          The ctags and etags programs (hereinafter collectively referred to as
          ctags, except where distinguished) generate an index (or "tag") file
          for a variety of language objects found in file(s).  This tag file
          allows these items to be quickly and easily located by a text editor
          or other utility. A "tag" signifies a language object for which an
          index entry is available (or, alternatively, the index entry created
          for that object).

          Alternatively, ctags can generate a cross reference file which lists,
          in human readable form, information about the various source objects
          found in a set of language files.

          Tag index files are supported by numerous editors, which allow the
          user to locate the object associated with a name appearing in a source
          file and jump to the file and line which defines the name. Those known
          about at the time of this release are:

              Vi(1) and its derivatives (e.g. Elvis, Vim, Vile, Lemmy), CRiSP,
              Emacs, FTE (Folding Text Editor), JED, jEdit, Mined, NEdit
              (Nirvana Edit), TSE (The SemWare Editor), UltraEdit, WorkSpace,
              X2, Zeus

          Ctags is capable of generating different kinds of tags for each of
          many different languages. For a complete list of supported languages,
          the names by which they are recognized, and the kinds of tags which
          are generated for each, see the --list-languages and --list-kinds
          options.

     SOURCE FILES
          Unless the --language-force option is specified, the language of each
          source file is automatically selected based upon a mapping of file
          names to languages. The mappings in effect for each language may be
          display using the --list-maps option and may be changed using the
          --langmap option.  On platforms which support it, if the name of a

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          file is not mapped to a language and the file is executable, the first
          line of the file is checked to see if the file is a "#!" script for a
          recognized language.

          By default, all other files names are ignored. This permits running
          ctags on all files in either a single directory (e.g. "ctags *"), or
          on all files in an entire source directory tree (e.g. "ctags -R"),
          since only those files whose names are mapped to languages will be
          scanned.

          [The reason that .h extensions are mapped to C++ files rather than C
          files is because it is common to use .h extensions in C++, and no harm
          results in treating them as C++ files.]

     OPTIONS
          Despite the wealth of available options, defaults are set so that
          ctags is most commonly executed without any options (e.g. "ctags *",
          or "ctags -R"), which will create a tag file in the current directory
          for all recognized source files. The options described below are
          provided merely to allow custom tailoring to meet special needs.

          Note that spaces separating the single-letter options from their
          parameters are optional.

          Note also that the boolean parameters to the long form options (those
          beginning with "--" and that take a "[=yes|no]" parameter) may be
          omitted, in which case "=yes" is implied. (e.g. --sort is equivalent
          to --sort=yes). Note further that "=1" and "=on" are considered
          synonyms for "=yes", and that "=0" and "=off" are considered synonyms
          for "=no".

          Some options are either ignored or useful only when used while running
          in etags mode (see -e option). Such options will be noted.

          Most options may appear anywhere on the command line, affecting only
          those files which follow the option. A few options, however, must
          appear before the first file name and will be noted as such.

          Options taking language names will accept those names in either upper
          or lower case. See the --list-languages option for a complete list of
          the built-in language names.

          -a   Equivalent to --append.

          -B   Use backward searching patterns (e.g. ?pattern?). [Ignored in

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               etags mode]

          -e   Enable etags mode, which will create a tag file for use with the
               Emacs editor.  Alternatively, if ctags is invoked by a name
               containing the string "etags" (either by renaming, or creating a
               link to, the executable), etags mode will be enabled. This option
               must appear before the first file name.

          -f tagfile
               Use the name specified by tagfile for the tag file (default is
               "tags", or "TAGS" when running in etags mode). If tagfile is
               specified as "-", then the tag file is written to standard output
               instead. Ctags will stubbornly refuse to take orders if tagfile
               exists and its first line contains something other than a valid
               tags line. This will save your neck if you mistakenly type "ctags
               -f *.c", which would otherwise overwrite your first C file with
               the tags generated by the rest! It will also refuse to accept a
               multi-character file name which begins with a '-' (dash)
               character, since this most likely means that you left out the tag
               file name and this option tried to grab the next option as the
               file name. If you really want to name your output tag file
               "-ugly", specify it as "./-ugly". This option must appear before
               the first file name. If this option is specified more than once,
               only the last will apply.

          -F   Use forward searching patterns (e.g. /pattern/) (default).
               [Ignored in etags mode]

          -h list
               Specifies a list of file extensions, separated by periods, which
               are to be interpreted as include (or header) files. To indicate
               files having no extension, use a period not followed by a non-
               period character (e.g. ".", "..x", ".x."). This option only
               affects how the scoping of a particular kinds of tags is
               interpreted (i.e. whether or not they are considered as globally
               visible or visible only within the file in which they are
               defined); it does not map the extension to any particular
               language. Any tag which is located in a non-include file and
               cannot be seen (e.g. linked to) from another file is considered
               to have file-limited (e.g. static) scope. No kind of tag
               appearing in an include file will be considered to have file-
               limited scope. If the first character in the list is a plus sign,
               then the extensions in the list will be appended to the current
               list; otherwise, the list will replace the current list. See,
               also, the --file-scope option. The default list is

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                                     Version 5.8

               ".h.H.hh.hpp.hxx.h++.inc.def". To restore the default list,
               specify -h default. Note that if an extension supplied to this
               option is not already mapped to a particular language (see SOURCE
               FILES, above), you will also need to use either the --langmap or
               --language-force option.

          -I identifier-list
               Specifies a list of identifiers which are to be specially handled
               while parsing C and C++ source files. This option is specifically
               provided to handle special cases arising through the use of
               preprocessor macros. When the identifiers listed are simple
               identifiers, these identifiers will be ignored during parsing of
               the source files. If an identifier is suffixed with a '+'
               character, ctags will also ignore any parenthesis-enclosed
               argument list which may immediately follow the identifier in the
               source files. If two identifiers are separated with the '='
               character, the first identifiers is replaced by the second
               identifiers for parsing purposes. The list of identifiers may be
               supplied directly on the command line or read in from a separate
               file. If the first character of identifier-list is '@', '.' or a
               pathname separator ('/' or '\'), or the first two characters
               specify a drive letter (e.g. "C:"), the parameter identifier-list
               will be interpreted as a filename from which to read a list of
               identifiers, one per input line. Otherwise, identifier-list is a
               list of identifiers (or identifier pairs) to be specially
               handled, each delimited by a either a comma or by white space (in
               which case the list should be quoted to keep the entire list as
               one command line argument). Multiple -I options may be supplied.
               To clear the list of ignore identifiers, supply a single dash
               ("-") for identifier-list.

               This feature is useful when preprocessor macros are used in such
               a way that they cause syntactic confusion due to their presence.
               Indeed, this is the best way of working around a number of
               problems caused by the presence of syntax-busting macros in
               source files (see CAVEATS, below). Some examples will illustrate
               this point.

                  int foo ARGDECL4(void *, ptr, long int, nbytes)

               In the above example, the macro "ARGDECL4" would be mistakenly
               interpreted to be the name of the function instead of the correct
               name of "foo". Specifying -I ARGDECL4 results in the correct
               behavior.

                  /* creates an RCS version string in module */
                  MODULE_VERSION("$Revision: 690 $")

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               In the above example the macro invocation looks too much like a
               function definition because it is not followed by a semicolon
               (indeed, it could even be followed by a global variable
               definition that would look much like a K&R style function
               parameter declaration). In fact, this seeming function definition
               could possibly even cause the rest of the file to be skipped over
               while trying to complete the definition. Specifying -I
               MODULE_VERSION+ would avoid such a problem.

                  CLASS Example {
                      // your content here
                  };

               The example above uses "CLASS" as a preprocessor macro which
               expands to something different for each platform. For instance
               CLASS may be defined as "class __declspec(dllexport)" on Win32
               platforms and simply "class" on UNIX.  Normally, the absence of
               the C++ keyword "class" would cause the source file to be
               incorrectly parsed. Correct behavior can be restored by
               specifying -I CLASS=class.

          -L file
               Read from file a list of file names for which tags should be
               generated.  If file is specified as "-", then file names are read
               from standard input. File names read using this option are
               processed following file names appearing on the command line.
               Options are also accepted in this input. If this option is
               specified more than once, only the last will apply. Note: file is
               read in line-oriented mode, where a new line is the only
               delimiter and non-trailing white space is considered significant,
               in order that file names containing spaces may be supplied
               (however, trailing white space is stripped from lines); this can
               affect how options are parsed if included in the input.

          -n   Equivalent to --excmd=number.

          -N   Equivalent to --excmd=pattern.

          -o tagfile
               Equivalent to -f tagfile.

          -R   Equivalent to --recurse.

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                                     Version 5.8

          -u   Equivalent to --sort=no (i.e. "unsorted").

          -V   Equivalent to --verbose.

          -w   This option is silently ignored for backward-compatibility with
               the ctags of SVR4 Unix.

          -x   Print a tabular, human-readable cross reference (xref) file to
               standard output instead of generating a tag file. The information
               contained in the output includes: the tag name; the kind of tag;
               the line number, file name, and source line (with extra white
               space condensed) of the file which defines the tag. No tag file
               is written and all options affecting tag file output will be
               ignored. Example applications for this feature are generating a
               listing of all functions located in a source file (e.g. ctags -x
               --c-kinds=f file), or generating a list of all externally visible
               global variables located in a source file (e.g. ctags -x
               --c-kinds=v --file-scope=no file). This option must appear before
               the first file name.

          --append[=yes|no]
               Indicates whether tags generated from the specified files should
               be appended to those already present in the tag file or should
               replace them. This option is off by default. This option must
               appear before the first file name.

          --etags-include=file
               Include a reference to file in the tag file. This option may be
               specified as many times as desired. This supports Emacs'
               capability to use a tag file which "includes" other tag files.
               [Available only in etags mode]

          --exclude=[pattern]
               Add pattern to a list of excluded files and directories. This
               option may be specified as many times as desired. For each file
               name considered by ctags, each pattern specified using this
               option will be compared against both the complete path (e.g.
               some/path/base.ext) and the base name (e.g. base.ext) of the
               file, thus allowing patterns which match a given file name
               irrespective of its path, or match only a specific path. If
               appropriate support is available from the runtime library of your
               C compiler, then pattern may contain the usual shell wildcards
               (not regular expressions) common on Unix (be sure to quote the

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                                     Version 5.8

               option parameter to protect the wildcards from being expanded by
               the shell before being passed to ctags; also be aware that
               wildcards can match the slash character, '/'). You can determine
               if shell wildcards are available on your platform by examining
               the output of the --version option, which will include
               "+wildcards" in the compiled feature list; otherwise, pattern is
               matched against file names using a simple textual comparison.

               If pattern begins with the character '@', then the rest of the
               string is interpreted as a file name from which to read exclusion
               patterns, one per line. If pattern is empty, the list of excluded
               patterns is cleared.  Note that at program startup, the default
               exclude list contains "EIFGEN", "SCCS", "RCS", and "CVS", which
               are names of directories for which it is generally not desirable
               to descend while processing the --recurse option.

          --excmd=type
               Determines the type of EX command used to locate tags in the
               source file.  [Ignored in etags mode]

               The valid values for type (either the entire word or the first
               letter is accepted) are:

               number   Use only line numbers in the tag file for locating tags.
                        This has four advantages:
                        1.  Significantly reduces the size of the resulting tag
                            file.
                        2.  Eliminates failures to find tags because the line
                            defining the tag has changed, causing the pattern
                            match to fail (note that some editors, such as vim,
                            are able to recover in many such instances).
                        3.  Eliminates finding identical matching, but
                            incorrect, source lines (see BUGS, below).
                        4.  Retains separate entries in the tag file for lines
                            which are identical in content. In pattern mode,
                            duplicate entries are dropped because the search
                            patterns they generate are identical, making the
                            duplicate entries useless.

                        However, this option has one significant drawback:
                        changes to the source files can cause the line numbers
                        recorded in the tag file to no longer correspond to the
                        lines in the source file, causing jumps to some tags to
                        miss the target definition by one or more lines.
                        Basically, this option is best used when the source code
                        to which it is applied is not subject to change.

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                        Selecting this option type causes the following options
                        to be ignored: -BF.

               pattern  Use only search patterns for all tags, rather than the
                        line numbers usually used for macro definitions. This
                        has the advantage of not referencing obsolete line
                        numbers when lines have been added or removed since the
                        tag file was generated.

               mixed    In this mode, patterns are generally used with a few
                        exceptions. For C, line numbers are used for macro
                        definition tags. This was the default format generated
                        by the original ctags and is, therefore, retained as the
                        default for this option. For Fortran, line numbers are
                        used for common blocks because their corresponding
                        source lines are generally identical, making pattern
                        searches useless for finding all matches.

          --extra=[+|-]flags
               Specifies whether to include extra tag entries for certain kinds
               of information. The parameter flags is a set of one-letter flags,
               each representing one kind of extra tag entry to include in the
               tag file. If flags is preceded by by either the '+' or '-'
               character, the effect of each flag is added to, or removed from,
               those currently enabled; otherwise the flags replace any current
               settings. The meaning of each flag is as follows:

                  f   Include an entry for the base file name of every source
                      file (e.g.  "example.c"), which addresses the first line
                      of the file.

                  q   Include an extra class-qualified tag entry for each tag
                      which is a member of a class (for languages for which this
                      information is extracted; currently C++, Eiffel, and
                      Java). The actual form of the qualified tag depends upon
                      the language from which the tag was derived (using a form
                      that is most natural for how qualified calls are specified
                      in the language). For C++, it is in the form
                      "class::member"; for Eiffel and Java, it is in the form
                      "class.member". This may allow easier location of a
                      specific tags when multiple occurrences of a tag name
                      occur in the tag file. Note, however, that this could
                      potentially more than double the size of the tag file.

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          --fields=[+|-]flags
               Specifies the available extension fields which are to be included
               in the entries of the tag file (see TAG FILE FORMAT, below, for
               more information). The parameter flags is a set of one-letter
               flags, each representing one type of extension field to include,
               with the following meanings (disabled by default unless
               indicated):

                  a   Access (or export) of class members
                  f   File-restricted scoping [enabled]
                  i   Inheritance information
                  k   Kind of tag as a single letter [enabled]
                  K   Kind of tag as full name
                  l   Language of source file containing tag
                  m   Implementation information
                  n   Line number of tag definition
                  s   Scope of tag definition [enabled]
                  S   Signature of routine (e.g. prototype or parameter list)
                  z   Include the "kind:" key in kind field
                  t   Type and name of a variable or typedef as "typeref:" field
                      [enabled]

               Each letter or group of letters may be preceded by either '+' to
               add it to the default set, or '-' to exclude it. In the absence
               of any preceding '+' or '-' sign, only those kinds explicitly
               listed in flags will be included in the output (i.e. overriding
               the default set). This option is ignored if the option --format=1
               has been specified. The default value of this option is fkst.

          --file-scope[=yes|no]
               Indicates whether tags scoped only for a single file (i.e. tags
               which cannot be seen outside of the file in which they are
               defined, such as "static" tags) should be included in the output.
               See, also, the -h option. This option is enabled by default.

          --filter[=yes|no]
               Causes ctags to behave as a filter, reading source file names
               from standard input and printing their tags to standard output on
               a file-by-file basis. If --sorted is enabled, tags are sorted
               only within the source file in which they are defined. File names
               are read from standard input in line-oriented input mode (see
               note for -L option) and only after file names listed on the
               command line or from any file supplied using the -L option. When
               this option is enabled, the options -f, -o, and --totals are
               ignored. This option is quite esoteric and is disabled by
               default. This option must appear before the first file name.

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          --filter-terminator=string
               Specifies a string to print to standard output following the tags
               for each file name parsed when the --filter option is enabled.
               This may permit an application reading the output of ctags to
               determine when the output for each file is finished. Note that if
               the file name read is a directory and --recurse is enabled, this
               string will be printed only one once at the end of all tags found
               for by descending the directory. This string will always be
               separated from the last tag line for the file by its terminating
               newline.  This option is quite esoteric and is empty by default.
               This option must appear before the first file name.

          --format=level
               Change the format of the output tag file. Currently the only
               valid values for level are 1 or 2. Level 1 specifies the original
               tag file format and level 2 specifies a new extended format
               containing extension fields (but in a manner which retains
               backward-compatibility with original vi(1) implementations). The
               default level is 2. This option must appear before the first file
               name. [Ignored in etags mode]

          --help
               Prints to standard output a detailed usage description, and then
               exits.

          --if0[=yes|no]
               Indicates a preference as to whether code within an "#if 0"
               branch of a preprocessor conditional should be examined for non-
               macro tags (macro tags are always included). Because the intent
               of this construct is to disable code, the default value of this
               option is no. Note that this indicates a preference only and does
               not guarantee skipping code within an "#if 0" branch, since the
               fall-back algorithm used to generate tags when preprocessor
               conditionals are too complex follows all branches of a
               conditional. This option is disabled by default.

          --<LANG>-kinds=[+|-]kinds
               Specifies a list of language-specific kinds of tags (or kinds) to
               include in the output file for a particular language, where
               <LANG> is case-insensitive and is one of the built-in language
               names (see the --list-languages option for a complete list). The
               parameter kinds is a group of one-letter flags designating kinds
               of tags (particular to the language) to either include or exclude
               from the output. The specific sets of flags recognized for each
               language, their meanings and defaults may be list using the

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               --list-kinds option. Each letter or group of letters may be
               preceded by either '+' to add it to, or '-' to remove it from,
               the default set. In the absence of any preceding '+' or '-' sign,
               only those kinds explicitly listed in kinds will be included in
               the output (i.e.  overriding the default for the specified
               language).

               As an example for the C language, in order to add prototypes and
               external variable declarations to the default set of tag kinds,
               but exclude macros, use --c-kinds=+px-d; to include only tags for
               functions, use --c-kinds=f.

          --langdef=name
               Defines a new user-defined language, name, to be parsed with
               regular expressions. Once defined, name may be used in other
               options taking language names. The typical use of this option is
               to first define the language, then map file names to it using
               --langmap, then specify regular expressions using --regex-<LANG>
               to define how its tags are found.

          --langmap=map[,map[...]]
               Controls how file names are mapped to languages (see the
               --list-maps option). Each comma-separated map consists of the
               language name (either a built-in or user-defined language), a
               colon, and a list of file extensions and/or file name patterns. A
               file extension is specified by preceding the extension with a
               period (e.g. ".c"). A file name pattern is specified by enclosing
               the pattern in parentheses (e.g. "([Mm]akefile)"). If appropriate
               support is available from the runtime library of your C compiler,
               then the file name pattern may contain the usual shell wildcards
               common on Unix (be sure to quote the option parameter to protect
               the wildcards from being expanded by the shell before being
               passed to ctags). You can determine if shell wildcards are
               available on your platform by examining the output of the
               --version option, which will include "+wildcards" in the compiled
               feature list; otherwise, the file name patterns are matched
               against file names using a simple textual comparison. When
               mapping a file extension, it will first be unmapped from any
               other languages.

               If the first character in a map is a plus sign, then the
               extensions and file name patterns in that map will be appended to
               the current map for that language; otherwise, the map will
               replace the current map. For example, to specify that only files
               with extensions of .c and .x are to be treated as C language
               files, use "--langmap=c:.c.x"; to also add files with extensions
               of .j as Java language files, specify

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               "--langmap=c:.c.x,java:+.j". To map makefiles (e.g. files named
               either "Makefile", "makefile", or having the extension ".mak") to
               a language called "make", specify
               "--langmap=make:([Mm]akefile).mak".  To map files having no
               extension, specify a period not followed by a non-period
               character (e.g. ".", "..x", ".x."). To clear the mapping for a
               particular language (thus inhibiting automatic generation of tags
               for that language), specify an empty extension list (e.g.
               "--langmap=fortran:"). To restore the default language mappings
               for all a particular language, supply the keyword "default" for
               the mapping.  To specify restore the default language mappings
               for all languages, specify "--langmap=default". Note that file
               extensions are tested before file name patterns when inferring
               the language of a file.

          --language-force=language
               By default, ctags automatically selects the language of a source
               file, ignoring those files whose language cannot be determined
               (see SOURCE FILES, above). This option forces the specified
               language (case-insensitive; either built-in or user-defined) to
               be used for every supplied file instead of automatically
               selecting the language based upon its extension. In addition, the
               special value auto indicates that the language should be
               automatically selected (which effectively disables this option).

          --languages=[+|-]list
               Specifies the languages for which tag generation is enabled, with
               list containing a comma-separated list of language names (case-
               insensitive; either built-in or user-defined). If the first
               language of list is not preceded by either a '+' or '-', the
               current list will be cleared before adding or removing the
               languages in list. Until a '-' is encountered, each language in
               the list will be added to the current list. As either the '+' or
               '-' is encountered in the list, the languages following it are
               added or removed from the current list, respectively. Thus, it
               becomes simple to replace the current list with a new one, or to
               add or remove languages from the current list. The actual list of
               files for which tags will be generated depends upon the language
               extension mapping in effect (see the --langmap option). Note that
               all languages, including user-defined languages are enabled
               unless explicitly disabled using this option. Language names
               included in list may be any built-in language or one previously
               defined with --langdef. The default is "all", which is also
               accepted as a valid argument. See the --list-languages option for
               a complete list of the built-in language names.

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          --license
               Prints a summary of the software license to standard output, and
               then exits.

          --line-directives[=yes|no]
               Specifies whether "#line" directives should be recognized. These
               are present in the output of preprocessors and contain the line
               number, and possibly the file name, of the original source
               file(s) from which the preprocessor output file was generated.
               When enabled, this option will cause ctags to generate tag
               entries marked with the file names and line numbers of their
               locations original source file(s), instead of their actual
               locations in the preprocessor output. The actual file names
               placed into the tag file will have the same leading path
               components as the preprocessor output file, since it is assumed
               that the original source files are located relative to the
               preprocessor output file (unless, of course, the #line directive
               specifies an absolute path). This option is off by default. Note:
               This option is generally only useful when used together with the
               --excmd=number (-n) option. Also, you may have to use either the
               --langmap or --language-force option if the extension of the
               preprocessor output file is not known to ctags.

          --links[=yes|no]
               Indicates whether symbolic links (if supported) should be
               followed. When disabled, symbolic links are ignored. This option
               is on by default.

          --list-kinds[=language|all]
               Lists the tag kinds recognized for either the specified language
               or all languages, and then exits. Each kind of tag recorded in
               the tag file is represented by a one-letter flag, which is also
               used to filter the tags placed into the output through use of the
               --<LANG>-kinds option. Note that some languages and/or tag kinds
               may be implemented using regular expressions and may not be
               available if regex support is not compiled into ctags (see the
               --regex-<LANG> option). Each kind listed is enabled unless
               followed by "[off]".

          --list-maps[=language|all]
               Lists the file extensions and file name patterns which associate
               a file name with a language for either the specified language or
               all languages, and then exits. See the --langmap option, and
               SOURCE FILES, above.

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     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

          --list-languages
               Lists the names of the languages understood by ctags, and then
               exits.  These language names are case insensitive and may be used
               in the --language-force, --languages, --<LANG>-kinds, and
               --regex-<LANG> options.

          --options=file
               Read additional options from file. The file should contain one
               option per line. As a special case, if --options=NONE is
               specified as the first option on the command line, it will
               disable the automatic reading of any configuration options from
               either a file or the environment (see FILES).

          --recurse[=yes|no]
               Recurse into directories encountered in the list of supplied
               files. If the list of supplied files is empty and no file list is
               specified with the -L option, then the current directory (i.e.
               ".") is assumed. Symbolic links are followed. If you don't like
               these behaviors, either explicitly specify the files or pipe the
               output of find(1) into ctags -L- instead. Note: This option is
               not supported on all platforms at present.  It is available if
               the output of the --help option includes this option.  See, also,
               the --exclude to limit recursion.

          --regex-<LANG>=/regexp/replacement/[kind-spec/][flags]
               The /regexp/replacement/ pair define a regular expression
               replacement pattern, similar in style to sed substitution
               commands, with which to generate tags from source files mapped to
               the named language, <LANG>, (case-insensitive; either a built-in
               or user-defined language). The regular expression, regexp,
               defines an extended regular expression (roughly that used by
               egrep(1)), which is used to locate a single source line
               containing a tag and may specify tab characters using \t. When a
               matching line is found, a tag will be generated for the name
               defined by replacement, which generally will contain the special
               back-references \1 through \9 to refer to matching sub-expression
               groups within regexp. The '/' separator characters shown in the
               parameter to the option can actually be replaced by any
               character. Note that whichever separator character is used will
               have to be escaped with a backslash ('\') character wherever it
               is used in the parameter as something other than a separator. The
               regular expression defined by this option is added to the current
               list of regular expressions for the specified language unless the
               parameter is omitted, in which case the current list is cleared.

               Unless modified by flags, regexp is interpreted as a Posix

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                                     Version 5.8

               extended regular expression. The replacement should expand for
               all matching lines to a non-empty string of characters, or a
               warning message will be reported. An optional kind specifier for
               tags matching regexp may follow replacement, which will determine
               what kind of tag is reported in the "kind" extension field (see
               TAG FILE FORMAT, below). The full form of kind-spec is in the
               form of a single letter, a comma, a name (without spaces), a
               comma, a description, followed by a separator, which specify the
               short and long forms of the kind value and its textual
               description (displayed using --list-kinds). Either the kind name
               and/or the description may be omitted. If kind-spec is omitted,
               it defaults to "r,regex". Finally, flags are one or more single-
               letter characters having the following effect upon the
               interpretation of regexp:

                  b   The pattern is interpreted as a Posix basic regular
                      expression.

                  e   The pattern is interpreted as a Posix extended regular
                      expression (default).

                  i   The regular expression is to be applied in a case-
                      insensitive manner.

               Note that this option is available only if ctags was compiled
               with support for regular expressions, which depends upon your
               platform. You can determine if support for regular expressions is
               compiled in by examining the output of the --version option,
               which will include "+regex" in the compiled feature list.

               For more information on the regular expressions used by ctags,
               see either the regex(5,7) man page, or the GNU info documentation
               for regex (e.g. "info regex").

          --sort[=yes|no|foldcase]
               Indicates whether the tag file should be sorted on the tag name
               (default is yes). Note that the original vi(1) required sorted
               tags. The foldcase value specifies case insensitive (or case-
               folded) sorting.  Fast binary searches of tag files sorted with
               case-folding will require special support from tools using tag
               files, such as that found in the ctags readtags library, or Vim
               version 6.2 or higher (using "set ignorecase"). This option must
               appear before the first file name. [Ignored in etags mode]

          --tag-relative[=yes|no]
               Indicates that the file paths recorded in the tag file should be

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                                     Version 5.8

               relative to the directory containing the tag file, rather than
               relative to the current directory, unless the files supplied on
               the command line are specified with absolute paths. This option
               must appear before the first file name. The default is yes when
               running in etags mode (see the -e option), no otherwise.

          --totals[=yes|no]
               Prints statistics about the source files read and the tag file
               written during the current invocation of ctags. This option is
               off by default.  This option must appear before the first file
               name.

          --verbose[=yes|no]
               Enable verbose mode. This prints out information on option
               processing and a brief message describing what action is being
               taken for each file considered by ctags. Normally, ctags does not
               read command line arguments until after options are read from the
               configuration files (see FILES, below) and the CTAGS environment
               variable. However, if this option is the first argument on the
               command line, it will take effect before any options are read
               from these sources. The default is no.

          --version
               Prints a version identifier for ctags to standard output, and
               then exits. This is guaranteed to always contain the string
               "Exuberant Ctags".

     OPERATIONAL DETAILS
          As ctags considers each file name in turn, it tries to determine the
          language of the file by applying the following three tests in order:
          if the file extension has been mapped to a language, if the file name
          matches a shell pattern mapped to a language, and finally if the file
          is executable and its first line specifies an interpreter using the
          Unix-style "#!" specification (if supported on the platform). If a
          language was identified, the file is opened and then the appropriate
          language parser is called to operate on the currently open file. The
          parser parses through the file and adds an entry to the tag file for
          each language object it is written to handle. See TAG FILE FORMAT,
          below, for details on these entries.

          This implementation of ctags imposes no formatting requirements on C
          code as do legacy implementations. Older implementations of ctags
          tended to rely upon certain formatting assumptions in order to help it
          resolve coding dilemmas caused by preprocessor conditionals.

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     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

          In general, ctags tries to be smart about conditional preprocessor
          directives. If a preprocessor conditional is encountered within a
          statement which defines a tag, ctags follows only the first branch of
          that conditional (except in the special case of "#if 0", in which case
          it follows only the last branch). The reason for this is that failing
          to pursue only one branch can result in ambiguous syntax, as in the
          following example:

               #ifdef TWO_ALTERNATIVES
               struct {
               #else
               union {
               #endif
                   short a;
                   long b;
               }

          Both branches cannot be followed, or braces become unbalanced and
          ctags would be unable to make sense of the syntax.

          If the application of this heuristic fails to properly parse a file,
          generally due to complicated and inconsistent pairing within the
          conditionals, ctags will retry the file using a different heuristic
          which does not selectively follow conditional preprocessor branches,
          but instead falls back to relying upon a closing brace ("}") in column
          1 as indicating the end of a block once any brace imbalance results
          from following a #if conditional branch.

          Ctags will also try to specially handle arguments lists enclosed in
          double sets of parentheses in order to accept the following
          conditional construct:

               extern void foo __ARGS((int one, char two));

          Any name immediately preceding the "((" will be automatically ignored
          and the previous name will be used.

          C++ operator definitions are specially handled. In order for
          consistency with all types of operators (overloaded and conversion),
          the operator name in the tag file will always be preceded by the
          string "operator " (i.e. even if the actual operator definition was
          written as "operator<<").

          After creating or appending to the tag file, it is sorted by the tag
          name, removing identical tag lines.

     TAG FILE FORMAT

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                                     Version 5.8

          When not running in etags mode, each entry in the tag file consists of
          a separate line, each looking like this in the most general case:

           tag_name<TAB>file_name<TAB>ex_cmd;"<TAB>extension_fields

          The fields and separators of these lines are specified as follows:

              1.  tag name
              2.  single tab character
              3.  name of the file in which the object associated with the tag
                  is located
              4.  single tab character
              5.  EX command used to locate the tag within the file; generally a
                  search pattern (either /pattern/ or ?pattern?) or line number
                  (see --excmd). Tag file format 2 (see --format) extends this
                  EX command under certain circumstances to include a set of
                  extension fields (described below) embedded in an EX comment
                  immediately appended to the EX command, which leaves it
                  backward-compatible with original vi(1) implementations.

          A few special tags are written into the tag file for internal
          purposes. These tags are composed in such a way that they always sort
          to the top of the file.  Therefore, the first two characters of these
          tags are used a magic number to detect a tag file for purposes of
          determining whether a valid tag file is being overwritten rather than
          a source file.

          Note that the name of each source file will be recorded in the tag
          file exactly as it appears on the command line. Therefore, if the path
          you specified on the command line was relative to the current
          directory, then it will be recorded in that same manner in the tag
          file. See, however, the --tag-relative option for how this behavior
          can be modified.

          Extension fields are tab-separated key-value pairs appended to the end
          of the EX command as a comment, as described above. These key value
          pairs appear in the general form "key:value". Their presence in the
          lines of the tag file are controlled by the --fields option. The
          possible keys and the meaning of their values are as follows:

          access      Indicates the visibility of this class member, where value
                      is specific to the language.

          file        Indicates that the tag has file-limited visibility. This
                      key has no corresponding value.

                                       - 18 -       Formatted:  February 7, 2018

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     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

          kind        Indicates the type, or kind, of tag. Its value is either
                      one of the corresponding one-letter flags described under
                      the various --<LANG>-kinds options above, or a full name.
                      It is permitted (and is, in fact, the default) for the key
                      portion of this field to be omitted. The optional
                      behaviors are controlled with the --fields option.

          implementation
                      When present, this indicates a limited implementation
                      (abstract vs. concrete) of a routine or class, where value
                      is specific to the language ("virtual" or "pure virtual"
                      for C++; "abstract" for Java).

          inherits    When present, value. is a comma-separated list of classes
                      from which this class is derived (i.e. inherits from).

          signature   When present, value is a language-dependent representation
                      of the signature of a routine. A routine signature in its
                      complete form specifies the return type of a routine and
                      its formal argument list. This extension field is
                      presently supported only for C-based languages and does
                      not include the return type.

          In addition, information on the scope of the tag definition may be
          available, with the key portion equal to some language-dependent
          construct name and its value the name declared for that construct in
          the program. This scope entry indicates the scope in which the tag was
          found. For example, a tag generated for a C structure member would
          have a scope looking like "struct:myStruct".

     HOW TO USE WITH VI
          Vi will, by default, expect a tag file by the name "tags" in the
          current directory. Once the tag file is built, the following commands
          exercise the tag indexing feature:

          vi -t tag   Start vi and position the cursor at the file and line
                      where "tag" is defined.

          :ta tag     Find a tag.

          Ctrl-]      Find the tag under the cursor.

          Ctrl-T      Return to previous location before jump to tag (not widely

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     CTAGS(1)                      Darren Hiebert                       CTAGS(1)
     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

                      implemented).

     HOW TO USE WITH GNU EMACS
          Emacs will, by default, expect a tag file by the name "TAGS" in the
          current directory. Once the tag file is built, the following commands
          exercise the tag indexing feature:

          M-x visit-tags-table <RET> FILE <RET>
                    Select the tag file, "FILE", to use.

          M-. [TAG] <RET>
                    Find the first definition of TAG. The default tag is the
                    identifier under the cursor.

          M-*       Pop back to where you previously invoked "M-.".

          C-u M-.   Find the next definition for the last tag.

          For more commands, see the Tags topic in the Emacs info document.

     HOW TO USE WITH NEDIT
          NEdit version 5.1 and later can handle the new extended tag file
          format (see --format). To make NEdit use the tag file, select
          "File->Load Tags File". To jump to the definition for a tag, highlight
          the word, the press Ctrl-D. NEdit 5.1 can can read multiple tag files
          from different directories.  Setting the X resource nedit.tagFile to
          the name of a tag file instructs NEdit to automatically load that tag
          file at startup time.

     CAVEATS
          Because ctags is neither a preprocessor nor a compiler, use of
          preprocessor macros can fool ctags into either missing tags or
          improperly generating inappropriate tags. Although ctags has been
          designed to handle certain common cases, this is the single biggest
          cause of reported problems. In particular, the use of preprocessor
          constructs which alter the textual syntax of C can fool ctags. You can
          work around many such problems by using the -I option.

          Note that since ctags generates patterns for locating tags (see the
          --excmd option), it is entirely possible that the wrong line may be
          found by your editor if there exists another source line which is
          identical to the line containing the tag. The following example

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     CTAGS(1)                      Darren Hiebert                       CTAGS(1)
     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

          demonstrates this condition:

               int variable;

               /* ... */
               void foo(variable)
               int variable;
               {
                   /* ... */
               }

          Depending upon which editor you use and where in the code you happen
          to be, it is possible that the search pattern may locate the local
          parameter declaration in foo() before it finds the actual global
          variable definition, since the lines (and therefore their search
          patterns are identical). This can be avoided by use of the --excmd=n
          option.

     BUGS
          Ctags has more options than ls(1).

          When parsing a C++ member function definition (e.g.
          "className::function"), ctags cannot determine whether the scope
          specifier is a class name or a namespace specifier and always lists it
          as a class name in the scope portion of the extension fields. Also, if
          a C++ function is defined outside of the class declaration (the usual
          case), the access specification (i.e. public, protected, or private)
          and implementation information (e.g. virtual, pure virtual) contained
          in the function declaration are not known when the tag is generated
          for the function definition. It will, however be available for
          prototypes (e.g --c++-kinds=+p).

          No qualified tags are generated for language objects inherited into a
          class.

     ENVIRONMENT VARIABLES
          CTAGS   If this environment variable exists, it will be expected to
                  contain a set of default options which are read when ctags
                  starts, after the configuration files listed in FILES, below,
                  are read, but before any command line options are read.
                  Options appearing on the command line will override options
                  specified in this variable. Only options will be read from
                  this variable. Note that all white space in this variable is
                  considered a separator, making it impossible to pass an option
                  parameter containing an embedded space. If this is a problem,

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     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

                  use a configuration file instead.

          ETAGS   Similar to the CTAGS variable above, this variable, if found,
                  will be read when etags starts. If this variable is not found,
                  etags will try to use CTAGS instead.

          TMPDIR  On Unix-like hosts where mkstemp() is available, the value of
                  this variable specifies the directory in which to place
                  temporary files. This can be useful if the size of a temporary
                  file becomes too large to fit on the partition holding the
                  default temporary directory defined at compilation time.
                  ctags creates temporary files only if either (1) an emacs-
                  style tag file is being generated, (2) the tag file is being
                  sent to standard output, or (3) the program was compiled to
                  use an internal sort algorithm to sort the tag files instead
                  of the the sort utility of the operating system. If the sort
                  utility of the operating system is being used, it will
                  generally observe this variable also. Note that if ctags is
                  setuid, the value of TMPDIR will be ignored.

     FILES
          /ctags.cnf (on MSDOS, MSWindows only)
          /etc/ctags.conf
          /usr/local/etc/ctags.conf
          $HOME/.ctags
          $HOME/ctags.cnf (on MSDOS, MSWindows only)
          .ctags
          ctags.cnf (on MSDOS, MSWindows only)
               If any of these configuration files exist, each will be expected
               to contain a set of default options which are read in the order
               listed when ctags starts, but before the CTAGS environment
               variable is read or any command line options are read. This makes
               it possible to set up site-wide, personal or project-level
               defaults. It is possible to compile ctags to read an additional
               configuration file before any of those shown above, which will be
               indicated if the output produced by the --version option lists
               the "custom-conf" feature. Options appearing in the CTAGS
               environment variable or on the command line will override options
               specified in these files. Only options will be read from these
               files. Note that the option files are read in line-oriented mode
               in which spaces are significant (since shell quoting is not
               possible). Each line of the file is read as one command line
               parameter (as if it were quoted with single quotes). Therefore,
               use new lines to indicate separate command-line arguments.

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     CTAGS(1)                      Darren Hiebert                       CTAGS(1)
     Exuberant Ctags                                             Exuberant Ctags

                                     Version 5.8

          tags The default tag file created by ctags.

          TAGS The default tag file created by etags.

     SEE ALSO
          The official Exuberant Ctags web site at:

               http://ctags.sourceforge.net

          Also ex(1), vi(1), elvis, or, better yet, vim, the official editor of
          ctags. For more information on vim, see the VIM Pages web site at:

               http://www.vim.org/

     AUTHOR
          Darren Hiebert <dhiebert at users.sourceforge.net>
          http://DarrenHiebert.com/

     MOTIVATION
          "Think ye at all times of rendering some service to every member of
          the human race."

          "All effort and exertion put forth by man from the fullness of his
          heart is worship, if it is prompted by the highest motives and the
          will to do service to humanity."

               -- From the Baha'i Writings

     CREDITS
          This version of ctags was originally derived from and inspired by the
          ctags program by Steve Kirkendall <kirkenda@cs.pdx.edu> that comes
          with the Elvis vi clone (though virtually none of the original code
          remains).

          Credit is also due Bram Moolenaar <Bram@vim.org>, the author of vim,
          who has devoted so much of his time and energy both to developing the
          editor as a service to others, and to helping the orphans of Uganda.

          The section entitled "HOW TO USE WITH GNU EMACS" was shamelessly
          stolen from the info page for GNU etags.

                                       - 23 -       Formatted:  February 7, 2018