NAME

       ctags-incompatibilities - Incompatibilities between Universal Ctags and Exuberant Ctags

SYNOPSIS

       ctags [options] [file(s)]
       etags [options] [file(s)]

DESCRIPTION

       This page describes major incompatible changes introduced to Universal Ctags forked from Exuberant Ctags.

   Option files loading at starting up time (preload files)
       Universal  Ctags  doesn't  load  ~/.ctags at starting up time.  File paths for preload files are changed.
       See "FILES" section of ctags(1).

   Environment variables for arranging command lines
       Universal Ctags doesn't read CTAGS and/or ETAGS environment variables.

   Incompatibilities in command line interface
   Ordering in a command line
       The command line format of Universal Ctags is "ctags [options] [source_file(s)]" following  the  standard
       POSIX convention.

       Exuberant Ctags accepts a option following a source file.

          $ ctags -o - foo.c --list-kinds=Sh
          f  functions

       Universal Ctags warns and ignores the option --list-kinds=Sh as follows.

          $ ctags -o - foo.c --list-kinds=Sh
          ctags: Warning: cannot open input file "--list-kinds=Sh" : No such file or directory
          a       foo.c   /^void a () {}$/;"      f       typeref:typename:void
          b       foo.c   /^void b () {}$/;"      f       typeref:typename:void

   The order of application of patterns and extensions in --langmap
       When  applying  mappings  for a name of given source file, Exuberant Ctags tests file name patterns AFTER
       file extensions (e-map-order). Universal Ctags does this differently; it tests file name patterns  BEFORE
       file extensions (u-map-order).

       This incompatible change is introduced to deal with the following situation:

          • build.xml as a source file,

          • The Ant parser declares it handles a file name pattern build.xml, and

          • The XML parser declares it handles a file extension .xml.

       Which  parser  should  be  used for parsing build.xml?  The assumption of Universal Ctags is the user may
       want to use the Ant parser; the file name pattern it declares is more specific than  the  file  extension
       that the XML parser declares. However, e-map-order chooses the XML parser.

       So Universal Ctags uses the u-map-order even though it introduces an incompatibility.

       --list-map-extensions=<language> and --list-map-patterns=<language> options are helpful to verify and the
       file extensions and the file name patterns of given <language>.

   Remove --file-tags and --file-scope options
       Even in Exuberant Ctags,  --file-tags  is  not  documented  in  its  man  page.   Instead  of  specifying
       --file-tags or --file-tags=yes, use --extras=+f or --extras=+{inputFile}.

       Instead of specifying --file-tags=no, use --extras=-f or --extras=-{inputFile}.

       Universal Ctags introduces F/fileScope extra as the replacement for --file-scope option.

       Instead of specifying --file-tags or --file-tags=yes, use --extras=+F or --extras=+{fileScope}.

       Instead of specifying --file-tags=no, use --extras=-F or --extras=-{fileScope}.

   Incompatibilities in language and kind definitions
   Language name defined with --langdef=name option
       The  characters  you  can  use  are  more  restricted  than  Exuberant  Ctags.  For more details, see the
       description of --langdef=name in ctags-optlib(7).

   Obsoleting --<LANG>-kinds option
       Some options have <LANG> as parameterized parts in their name like --foo-<LANG>=... or  --<LANG>-foo=....
       The most of all such options in Exuberant Ctags have the former form, --foo-<LANG>=....  The exception is
       --<LANG>-kinds.

       Universal Ctags uses the former form for all <LANG> parameterized option. Use --kinds-<LANG>  instead  of
       --<LANG>-kinds in Universal Ctags. --<LANG>-kinds still works but it will be removed in the future.

       The former form may be friendly to shell completion engines.

   Disallowing to define a kind with file as name
       The  kind  name  file  is  reserved.   Using  it  as  part  of  kind spec in --regex-<LANG> option is now
       disallowed.

   Disallowing to define a kind with 'F' as letter
       The kind letter 'F' is reserved.  Using it as part of  a  kind  spec  in  --regex-<LANG>  option  is  now
       disallowed.

   Disallowing to use other than alphabetical character as kind letter
       Exuberant   Ctags   accepts   a   character   other   than  alphabetical  character  as  kind  letter  in
       --regex-<LANG>=... option.  Universal Ctags accepts only an alphabetical character.

   Acceptable characters as parts of a kind name
       Exuberant   Ctags   accepts   any   character   as   a   part   of   a    kind    name    defined    with
       --regex-<LANG>=/regex/replacement/kind-spec/.

       Universal  Ctags  accepts only an alphabetical character as the initial letter of a kind name.  Universal
       Ctags accepts only an alphabetical character or numerical character as the rest letters.

       An example:

          --regex-Foo=/abstract +class +([a-z]+)/\1/a,abstract class/i

       Universal Ctags rejects this because the kind name, abstract class, includes a whitespace character.

       This requirement is for making the output of Universal Ctags follow the tags file format.

   A combination of a kind letter and a kind name
       In Universal Ctags, the combination of a kind letter and a kind name must be unique in a language.

       You cannot define more than one kind reusing a kind letter with different kind names. You  cannot  define
       more than one kind reusing a kind name with different kind letters.

       An example:

          --regex-Foo=/abstract +class +([a-z]+)/\1/a,abstractClass/i
          --regex-Foo=/attribute +([a-z]+)/\1/a,attribute/i

       Universal  Ctags  rejects this because the kind letter, 'a', used twice for defining a kind abstractClass
       and attribute.

   Incompatibilities in tags file format
   Using numerical character in the name part of tag tagfield
       The version 2 tags file format, the default output format of Exuberant Ctags, accepts  only  alphabetical
       characters in the name part of tag tagfield.

       Universal  Ctags  introduces  an  exception  to  this  specification;  it may use numerical characters in
       addition to alphabetical characters as the letters other than initial letter of the name part.

       The kinds heading1, heading2, and heading3 in the HTML parser are the examples.

   Truncating the pattern for long input lines
       To prevent generating overly large tags files, a pattern field is truncated, by default,  when  its  size
       exceeds  96  bytes.  A  different limit can be specified with --pattern-length-limit=N. Specifying 0 as N
       results no truncation as Exuberant Ctags does not.

   Kind letters and names
       A kind letter 'F' and a kind name file are reserved in the  main  part.  A  parser  cannot  have  a  kind
       conflicting with these reserved ones. Some incompatible changes are introduced to follow the above rule.

       • Cobol's file kind is renamed to fileDesc because the kind name file is reserved.

       • Ruby's 'F' (singletonMethod) is changed to 'S'.

       • SQL's 'F' (field) is changed to 'E'.

SEE ALSO

       ctags(1), ctags-optlib(7), and tags(5).