ctags \- Generate tag files for source code

.TP 6

.TP 6

The \fBctags\fP and \fBetags\fP programs (hereinafter collectively referred to

as \fBctags\fP, except where distinguished) generate an index (or "tag") file

for a variety of language objects found in \fIfile(s)\fP.

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, \fBctags\fP 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:

.RS 4

\fBVi\fP(1) and its derivatives (e.g. Elvis, Vim, Vile, Lemmy),

\fBCRiSP\fP,

\fBEmacs\fP,

\fBFTE\fP (Folding Text Editor),

\fBJED\fP,

\fBjEdit\fP,

\fBMined\fP,

\fBNEdit\fP (Nirvana Edit),

\fBTSE\fP (The SemWare Editor),

\fBUltraEdit\fP,

\fBWorkSpace\fP,

\fBX2\fP,

.RE

\fBCtags\fP 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 \fB\-\-list\-languages\fP and \fB\-\-list\-kinds\fP options.

Unless the \fB\-\-language\-force\fP 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

\fB\-\-list\-maps\fP option and may be changed using the \fB\-\-langmap\fP 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

\fBctags\fP 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.]

Despite the wealth of available options, defaults are set so that \fBctags\fP

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 "\fI[=yes\fP|\fIno]\fP" parameter) may

be omitted, in which case "\fB=\fP\fIyes\fP" is implied. (e.g. \fB\-\-sort\fP

is equivalent to \fB\-\-sort\fP=\fIyes\fP). Note further that "=\fI1\fP" and

"=\fIon\fP" are considered synonyms for "=\fIyes\fP", and that "=\fI0\fP"

and "=\fIoff\fP" are considered synonyms for "=\fIno\fP".

Some options are either ignored or useful only when used while running in

etags mode (see \fB\-e\fP 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 \fB\-\-list\-languages\fP option for a complete list of the

built-in language names.

.TP 5

Equivalent to \fB\-\-append\fP.

.TP 5

Use backward searching patterns (e.g. ?pattern?). [Ignored in etags mode]

.TP 5

Enable etags mode, which will create a tag file for use with the Emacs editor.

Alternatively, if \fBctags\fP 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.

.TP 5

Use the name specified by \fItagfile\fP for the tag file (default is "tags",

or "TAGS" when running in etags mode). If \fItagfile\fP is specified as

"\-", then the tag file is written to standard output instead. \fBCtags\fP

will stubbornly refuse to take orders if \fItagfile\fP 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.

.TP 5

Use forward searching patterns (e.g. /pattern/) (default).

[Ignored in etags mode]

.TP 5

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 \fB\-\-file\-scope\fP option. The default list is

".h.H.hh.hpp.hxx.h++.inc.def". To restore the default list, specify \fB\-h\fP

\fIdefault\fP. Note that if an extension supplied to this option is not

already mapped to a particular language (see \fBSOURCE FILES\fP, above), you

will also need to use either the \fB\-\-langmap\fP or \fB\-\-language\-force\fP

option.

.TP 5

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, \fBctags\fP 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 \fIidentifier\-list\fP is '@', '.' or

a pathname separator ('/' or '\\'), or the first two characters specify a

drive letter (e.g. "C:"), the parameter \fIidentifier\-list\fP will be

interpreted as a filename from which to read a list of identifiers, one per

input line. Otherwise, \fIidentifier\-list\fP 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 \fB\-I\fP options may be supplied.

To clear the list of ignore identifiers, supply a single dash ("\-") for

\fIidentifier\-list\fP.

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 \fBCAVEATS\fP, below). Some

examples will illustrate this point.

.RS 8

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

.RE

.IP

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

\fB\-I\fP \fIARGDECL4\fP results in the correct behavior.

.RS 8

/* creates an RCS version string in module */

.br

MODULE_VERSION("$Revision$")

.RE

.IP

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 \fB\-I\fP \fIMODULE_VERSION+\fP would

avoid such a problem.

.RS 8

CLASS Example {

.br

// your content here

.br

};

.RE

.IP

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

\fB\-I\fP \fICLASS=class\fP.

.TP 5

Read from \fIfile\fP a list of file names for which tags should be generated.

If \fIfile\fP 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. \fBNote:\fP

\fIfile\fP 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.

.TP 5

Equivalent to \fB\-\-excmd\fP=\fInumber\fP.

.TP 5

Equivalent to \fB\-\-excmd\fP=\fIpattern\fP.

.TP 5

Equivalent to \fB\-f\fP \fItagfile\fP.

.TP 5

Equivalent to \fB\-\-recurse\fP.

.TP 5

Equivalent to \fB\-\-sort\fP=\fIno\fP (i.e. "unsorted").

.TP 5

Equivalent to \fB\-\-verbose\fP.

.TP 5

This option is silently ignored for backward-compatibility with the ctags

of SVR4 Unix.

.TP 5

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. \fBctags \-x \-\-c\-kinds\fP=\fIf\fP

\fIfile\fP), or generating a list of all externally visible global variables

located in a source file (e.g. \fBctags \-x \-\-c\-kinds\fP=\fIv\fP

\fB\-\-file\-scope\fP=\fIno file\fP). This option must appear before the first

file name.

.TP 5

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.

.TP 5

Include a reference to \fIfile\fP 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]

.TP 5

Add \fIpattern\fP to a list of excluded files and directories. This option

may be specified as many times as desired. For each file name considered by

\fBctags\fP, each \fIpattern\fP 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

\fIpattern\fP 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 \fBctags\fP; 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

\fB\-\-version\fP option, which will include "+wildcards" in the compiled

feature list; otherwise, \fIpattern\fP is matched against file names using a

simple textual comparison.

If \fIpattern\fP 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 \fIpattern\fP 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 \fB\-\-recurse\fP

option.

.TP 5

Determines the type of EX command used to locate tags in the source file.

[Ignored in etags mode]

The valid values for \fItype\fP (either the entire word or the first letter is

accepted) are:

.RS 5

.TP 9

Use only line numbers in the tag file for locating tags. This has four

advantages:

.PD 0

.RS 9

.TP 4

Significantly reduces the size of the resulting tag file.

.TP 4

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

\fBvim\fP, are able to recover in many such instances).

.TP 4

Eliminates finding identical matching, but incorrect, source lines (see

\fBBUGS\fP, below).

.TP 4

Retains separate entries in the tag file for lines which are identical in

content. In \fIpattern\fP mode, duplicate entries are dropped because the

search patterns they generate are identical, making the duplicate entries

useless.

.RE

.PD 1

.IP

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: \fB\-BF\fP.

.TP 9

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.

.TP 9

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 \fBctags\fP 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.

.RE

.TP 5

Specifies whether to include extra tag entries for certain kinds of

information. The parameter \fIflags\fP is a set of one-letter flags, each

representing one kind of extra tag entry to include in the tag file. If

\fIflags\fP 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:

.PP

.RS 8

.TP 4

Include an entry for the base file name of every source file (e.g.

"example.c"), which addresses the first line of the file.

.TP 4

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, Java, and Perl). 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++ and

Perl, 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. .RE

.RE

.TP 5

Specifies the available extension fields which are to be included in the

entries of the tag file (see \fBTAG FILE FORMAT\fP, below, for more

information). The parameter \fIflags\fP 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):

.PP

.PD 0

.RS 8

.TP 4

Access (or export) of class members

.TP 4

File-restricted scoping [enabled]

.TP 4

Inheritance information

.TP 4

Kind of tag as a single letter [enabled]

.TP 4

Kind of tag as full name

.TP 4

Language of source file containing tag

.TP 4

Implementation information

.TP 4

Line number of tag definition

.TP 4

Scope of tag definition [enabled]

.TP 4

Signature of routine (e.g. prototype or parameter list)

.TP 4

Include the "kind:" key in kind field

.TP 4

Type and name of a variable or typedef as "typeref:" field [enabled]

.PD 1

.RE

.RS 5

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 \fIflags\fP will be included in

the output (i.e. overriding the default set). All fields are included if '*'

is given. This option is ignored if the

option \fB\-\-format\fP=\fI1\fP has been specified. The default value

of this option is \fIfkst\fP.

.RE

.TP 5

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 \fB\-h\fP option. This option

is enabled by default.

.TP 5

Causes \fBctags\fP 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 \fB\-\-sorted\fP 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 \fB\-L\fP option) and only after file

names listed on the command line or from any file supplied using the \fB\-L\fP

option. When this option is enabled, the options \fB\-f\fP, \fB\-o\fP,

and \fB\-\-totals\fP are ignored. This option is quite esoteric and is disabled

by default. This option must appear before the first file name.

.TP 5

Specifies a string to print to standard output following the tags for each

file name parsed when the \fB\-\-filter\fP 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

\fB\-\-recurse\fP 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.

.TP 5

Change the format of the output tag file. Currently the only valid values for

\fIlevel\fP are \fI1\fP or \fI2\fP. 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

\fBvi\fP(1) implementations). The default level is 2. This option must appear

before the first file name. [Ignored in etags mode]

.TP 5

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

.TP 5

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 \fIno\fP. 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.

.TP 5

Specifies a list of language-specific kinds of tags (or kinds) to include in

the output file for a particular language, where \fB<LANG>\fP is

case-insensitive and is one of the built-in language names (see the

\fB\-\-list\-languages\fP option for a complete list). The parameter \fIkinds\fP

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 \fB\-\-list\-kinds\fP 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 \fIkinds\fP will be included in the output (i.e.

overriding the default for the specified language).

Specifies '*' as the parameter \fIkinds\fP to include all kinds implemented

in <LANG> in the output. Further more if '*' is given as <LANG>, specification

of the parameter \fIkinds\fP affects all languages defined in ctags.

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 \fB\-\-c\-kinds\fP=\fI+px\-d\fP; to include only tags for functions, use

\fB\-\-c\-kinds\fP=\fIf\fP.

.TP 5

Defines a new user-defined language, \fIname\fP, to be parsed with regular

expressions. Once defined, \fIname\fP 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 \fI\-\-langmap\fP, then specify

regular expressions using \fI\-\-regex\-<LANG>\fP to define how its tags are

found.

.TP 5

Controls how file names are mapped to languages (see the \fB\-\-list\-maps\fP

option). Each comma-separated \fImap\fP 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 \fBctags\fP). You can determine

if shell wildcards are available on your platform by examining the output of

the \fB\-\-version\fP 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 "\fB\-\-langmap\fP=\fIc:.c.x\fP"; to also add files with

extensions of .j as Java language files, specify

"\fB\-\-langmap\fP=\fIc:.c.x,java:+.j\fP". To map makefiles (e.g. files

named either "Makefile", "makefile", or having the extension ".mak") to a

language called "make", specify "\fB\-\-langmap\fP=\fImake:([Mm]akefile).mak\fP".

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.

"\fB\-\-langmap\fP=\fIfortran:\fP"). 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

"\fB\-\-langmap\fP=\fIdefault\fP". Note that file extensions are tested before

file name patterns when inferring the language of a file.

.TP 5

By default, \fBctags\fP automatically selects the language of a source file,

ignoring those files whose language cannot be determined (see

\fBSOURCE FILES\fP, above). This option forces the specified \fIlanguage\fP

(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 \fIauto\fP indicates that the

language should be automatically selected (which effectively disables this

option).

.TP 5

Specifies the languages for which tag generation is enabled, with \fIlist\fP

containing a comma-separated list of language names (case-insensitive; either

built-in or user-defined). If the first language of \fIlist\fP is not preceded

by either a '+' or '\-', the current list will be cleared before adding or

removing the languages in \fIlist\fP. 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 \fB\-\-langmap\fP

option). Note that all languages, including user-defined languages are enabled

unless explicitly disabled using this option. Language names included in

\fIlist\fP may be any built-in language or one previously defined with

\fB\-\-langdef\fP. The default is "all", which is also accepted as a valid

argument. See the \fB\-\-list\-languages\fP option for a complete list of the

built-in language names.

.TP 5

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

.TP 5

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 \fBctags\fP 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. \fBNote:\fP This option is

generally only useful when used together with the \fB\-\-excmd\fP=\fInumber\fP

(\fB\-n\fP) option. Also, you may have to use either the \fB\-\-langmap\fP or

\fB\-\-language\-force\fP option if the extension of the preprocessor output file

is not known to \fBctags\fP.

.TP 5

Indicates whether symbolic links (if supported) should be followed. When

disabled, symbolic links are ignored. This option is on by default.

.TP 5

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 \fB\-\-<LANG>\-kinds\fP 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 \fBctags\fP (see

the \fB\-\-regex\-<LANG>\fP option). Each kind listed is enabled unless followed

by "[off]".

.TP 5

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 \fB\-\-langmap\fP option, and \fBSOURCE FILES\fP, above.

.TP 5

Lists the names of the languages understood by \fBctags\fP, and then exits.

These language names are case insensitive and may be used in the

\fB\-\-language\-force\fP, \fB\-\-languages\fP, \fB\-\-<LANG>\-kinds\fP, and

\fB\-\-regex\-<LANG>\fP options.

.TP 5

Read additional options from \fIfile\fP or \fIdirectory\fP. If a file is

specified, it should contain one option per line. If a directory is

specified(and scandir function is available at build configuration time),

files suffixed with .ctags or .conf under the directory are read. (On MSDOS

or MSWindows this directory traverse feature is temporary disable because the

contributor of this feature has no access to the platfroms.

Volunters are welcome).

As a special case, if

\fB\-\-options\fP=\fINONE\fP 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 \fBFILES\fP).

.TP 5

Write fewer messages(default is \fIno\fP).

.TP 5

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

\fB\-L\fP 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 \fBfind\fP(1) into \fBctags \-L\-\fP

instead. \fBNote:\fP This option is not supported on all platforms at present.

It is available if the output of the \fB\-\-help\fP option includes this option.

See, also, the \fB\-\-exclude\fP to limit recursion.

.TP 5

The \fI/regexp/replacement/\fP pair define a regular expression replacement

pattern, similar in style to \fBsed\fP substitution commands, with which to

generate tags from source files mapped to the named language, \fB<LANG>\fP,

(case-insensitive; either a built-in or user-defined language). The regular

expression, \fIregexp\fP, defines an extended regular expression (roughly that

used by \fBegrep\fP(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

\fIreplacement\fP, which generally will contain the special back-references

\\1 through \\9 to refer to matching sub-expression groups within

\fIregexp\fP. 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 \fIflags\fP, \fIregexp\fP is interpreted as a Posix

extended regular expression. The \fIreplacement\fP 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 \fIregexp\fP may

follow \fIreplacement\fP, which will determine what kind of tag is reported in

the "kind" extension field (see \fBTAG FILE FORMAT\fP, below). The full form

of \fIkind\-spec\fP 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 \fB\-\-list\-kinds\fP). Either the kind name and/or the

description may be omitted. If \fIkind\-spec\fP is omitted, it defaults to

"\fIr,regex\fP". Finally, \fIflags\fP are one or more single-letter characters

having the following effect upon the interpretation of \fIregexp\fP:

.PP

.RS 8

.TP 4

The pattern is interpreted as a Posix basic regular expression.

.TP 4

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

.TP 4

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

.RE

.RS 5

Note that this option is available only if \fBctags\fP 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 \fB\-\-version\fP option, which will include "+regex" in the

compiled feature list.

For more information on the regular expressions used by \fBctags\fP, see

either the \fBregex(5,7)\fP man page, or the GNU info documentation for regex

(e.g. "info regex").

.RE

.TP 5

Indicates whether the tag file should be sorted on the tag name (default is

\fIyes\fP). Note that the original \fBvi\fP(1) required sorted tags.

The \fIfoldcase\fP 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]

.TP 5

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 \fIyes\fP when running in etags mode (see the \fB\-e\fP

option), \fIno\fP otherwise.

.TP 5

Prints statistics about the source files read and the tag file written during

the current invocation of \fBctags\fP. This option is off by default.

This option must appear before the first file name.

.TP 5

Specifies whether a macro tag should be generated from an #undef CPP directive

(in a C/C++ file), as if it were a #define directive. This option is enabled by

default.

.TP 5

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 \fBctags\fP. Normally, \fBctags\fP does not read command line arguments

until after options are read from the configuration files (see \fBFILES\fP,

below) and the \fBCTAGS\fP 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 \fIno\fP.

.TP 5

Prints a version identifier for \fBctags\fP to standard output, and then

exits. This is guaranteed to always contain the string "Exuberant Ctags".

As \fBctags\fP 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

\fBTAG FILE FORMAT\fP, below, for details on these entries.

This implementation of \fBctags\fP 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, \fBctags\fP tries to be smart about conditional preprocessor

directives. If a preprocessor conditional is encountered within a statement

which defines a tag, \fBctags\fP 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:

.RS

#ifdef TWO_ALTERNATIVES

.br

struct {

.br

#else

.br

union {

.br

#endif

.RS 4

short a;

.br

long b;

.RE

}

.RE

Both branches cannot be followed, or braces become unbalanced and \fBctags\fP

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,

\fBctags\fP 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.

\fBCtags\fP will also try to specially handle arguments lists enclosed in

double sets of parentheses in order to accept the following conditional

construct:

.RS

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

.RE

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.

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:

.RS 1

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

.RE

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

.PD 0

.RS 4

.TP 4

tag name

.TP 4

single tab character

.TP 4

name of the file in which the object associated with the tag is located

.TP 4

single tab character

.TP 4

EX command used to locate the tag within the file; generally a search pattern

(either /pattern/ or ?pattern?) or line number (see \fB\-\-excmd\fP). Tag file

format 2 (see \fB\-\-format\fP) 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 \fBvi\fP(1) implementations.

.RE

.PD 1

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

\fB\-\-tag\-relative\fP 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 "\fIkey\fP:\fIvalue\fP". Their presence in the lines of the

tag file are controlled by the \fB\-\-fields\fP option. The possible keys and

the meaning of their values are as follows:

.TP 12

Indicates the visibility of this class member, where \fIvalue\fP is specific

to the language.

.TP 12

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

corresponding value.

.TP 12

Indicates the type, or kind, of tag. Its value is either one of the

corresponding one-letter flags described under the various

\fB\-\-<LANG>\-kinds\fP 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 \fB\-\-fields\fP option.

.TP 12

When present, this indicates a limited implementation (abstract vs. concrete)

of a routine or class, where \fIvalue\fP is specific to the language

("virtual" or "pure virtual" for C++; "abstract" for Java).

.TP 12

When present, \fIvalue\fP. is a comma-separated list of classes from which

this class is derived (i.e. inherits from).

.TP 12

When present, \fIvalue\fP 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.

.PP

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".

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:

.TP 12

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

.TP 12

Find a tag.

.TP 12

Find the tag under the cursor.

.TP 12