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CTAGS(1)                                           Exuberant Ctags                                           CTAGS(1)



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) gen‐
       erate 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 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  recog‐
       nized  source files. The options described below are provided merely to allow custom tailoring to meet special
       needs.


       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 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 exe‐
            cutable), 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 ".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 particu‐
            lar  language  (see  SOURCE  FILES,  above),  you  will  also  need to use either the --langmap or --lan‐
            guage-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
            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 $")


            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  defini‐
            tion. 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  sim‐
            ply  "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.


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


            --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  com‐
            pared  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 spe‐
            cific 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
            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  sim‐
            ple 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 pat‐
                         tern mode, duplicate entries are dropped because the search patterns they generate are iden‐
                         tical, making the duplicate entries useless.



            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 com‐
                     mon 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  lan‐
                   guages  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.


       --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 repre‐
            senting 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]

            name.


       --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  par‐
            ticular  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  desig‐
            nating  kinds of tags (particular to the language) to either include or exclude from the output. The spe‐
            cific sets of flags recognized for each language, their meanings and  defaults  may  be  list  using  the
            --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.
            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
            "--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 lan‐
            guage 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  lan‐
            guage  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  lan‐
            guages  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 lan‐
            guages, including user-defined languages are enabled unless explicitly disabled using this  option.  Lan‐
            guage  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  com‐
            plete list of the built-in language names.


       --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 preproces‐
            sors 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 orig‐
            inal  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
            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.


       --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  read‐
            ing 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  parame‐
            ter is omitted, in which case the current list is cleared.

            Unless  modified  by flags, regexp is interpreted as a Posix 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 deter‐
            mine 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
            ining 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 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 argu‐
            ments until after options are read from the configuration files (see FILES, below) and the CTAGS environ‐
            ment  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 fol‐
       lowing 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  identi‐
       fied,  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.

       In  general,  ctags tries to be smart about conditional preprocessor directives. If a preprocessor conditional

       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 incon‐
       sistent 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  con‐
       ditional 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  (over‐
       loaded  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
       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 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  rou‐
                   tine 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 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-.".




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 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 defini‐
       tion,  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 por‐
       tion 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. vir‐
       tual, 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, use a configuration file instead.


       ETAGS   Similar to the CTAGS variable above, this variable, if found, will be read when etags starts. If  this


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  sin‐
              gle quotes). Therefore, use new lines to indicate separate command-line arguments.


       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



Darren Hiebert                                       Version 5.8                                             CTAGS(1)