xenial (1) ctags-exuberant.1.gz

Provided by: exuberant-ctags_5.9~svn20110310-11_amd64 bug

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 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 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
            ".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: 750 $")

            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.

       -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 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. 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 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.

       --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.

       --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 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 --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  "--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.

       --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.

       --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  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  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.

       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

       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.

       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 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,
       then  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 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, 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.

       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.