ctags (1)
NAME
ctags - Generate tag files for source code
SYNOPSIS
ctags [options] [file(s)]
etags [options] [file(s)]
DESCRIPTION
The ctags and etags programs (hereinafter collectively referred to as
ctags, except where distinguished) 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, NEdit (Nirvana Edit), TSE
(The SemWare Editor), 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 TAG KINDS, below.
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. 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. File names are mapped to languages according to
the following default mappings (which may be overridden with the
--langmap option):
Assembler
*.asm *.ASM *.[sS] *.A51 *.29[kK] *.[68][68][kKsSxX]
*.[xX][68][68]
ASP *.asp *.asa
Lisp *.cl *.clisp *.el *.l *.lisp *.lsp *.ml
Lua *.lua
Make *.mak [Mm]akefile*
Pascal *.p *.pas
Perl *.pl *.pm *.perl
PHP *.php *.php3 *.phtml
PL/SQL *.sql
Python *.py *.python
REXX *.cmd *.rexx *.rx
Ruby *.rb
Scheme *.sch *.scheme *.scm *.sm *.SCM *.SM
Shell scripts (Bourne/Korn/Z)
*.sh *.SH *.bsh *.bash *.ksh *.zsh
S-Lang *.sl
Tcl *.tcl *.wish
Vera *.vr *.vri *.vrh
Verilog *.v
Vim *.vim
YACC/Bison
*.y
By default, all other files names are ignored. This permits running
ctags on all files in either a single directory (e.g. "ctags *"), or
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 param-
eters 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 omit-
ted, 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 TAG KINDS for a complete list of the built-in lan-
-e Enable etags mode, which will create a tag file for use with the
Emacs editor. Alternatively, if ctags is invoked by a name con-
taining 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 spec-
ified 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
multicharacter 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 inter-
preted (i.e. whether or not they are considered as globally visi-
ble 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 char-
acter 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 sup-
plied to this option is not already mapped to a particular lan-
guage (see SOURCE FILES, above), you will also need to use either
the --langmap or --language-force option.
-I tokenlist
Specifies a list of tokens which are to be specially handled while
parsing C and C++ source files. This option is specifically pro-
vided to handle special cases arising through the use of prepro-
'\'), or the first two characters specify a drive letter (e.g.
"C:"), the parameter tokenlist will be interpreted as a filename
from which to read a list of tokens, one per input line. Other-
wise, tokenlist is a list of tokens (or token pairs) to be spe-
cially 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 tokens, supply a single dash
("-") for tokenlist.
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 prob-
lems caused by the presence of syntax-busting macros in source
files (see BUGS, 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: 1.21 $")
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 declara-
tion). 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 incor-
rectly 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 gen-
erated. If file is specified as "-", then file names are read
from standard input. File names read using this option are pro-
cessed following file names appearing on the command line. Options
all also accepted in this input. If this option is specified more
-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 backwards 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-types=f
file), or generating a list of all externally visible global vari-
ables located in a source file (e.g. ctags -x --c-types=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' capabil-
ity 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
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 pat-
terns they generate are identical, making the dupli-
cate 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. Basi-
cally, 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 defi-
nition tags. This was the default format generated by the
of information. The parameter flags is a set of one-letter flags,
each representing one kind of extra tag entry to include in the
tag file. If flags is preceded by by either the '+' or '-' charac-
ter, the effect of each flag is added to, or removed from, those
currently enabled; otherwise the flags replace any current set-
tings. 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 lan-
guage 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
occurrances of a tag name occur in the tag file. Note, how-
ever, 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 indi-
cated):
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 definintion
s Scope of tag definition [enabled]
s Signature of routine (e.g. prototype or parameter list)
z Include the "kind:" key in kind field
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.
--file-scope[=yes|no]
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 output 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 one once at the end of all tags found
for by descending the directory. This string will always be sepa-
rated from the last tag line for the file by its terminating new-
line. 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 compati-
bility 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.
--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 options is
no. Note that this indicates a preference only and does not guar-
antee 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>-types=[+|-]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 one of the built-in language names (see TAG KINDS, below, 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 is
functions, use --c-types=f.
--langdef=name
Defines a new user-defined language, name, to be parsed with regu-
lar 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 SOURCE FILES,
above). 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 paren-
theses (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 platfom 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 tex-
tual comparison.
If the first character in a map is a plus sign, then the exten-
sions 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 exten-
sions 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 hav-
ing the extension ".mak") to a language called "make", specify
"--langmap=make:([Mm]akefile).mak". To map files having no exten-
sion, 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=for-
tran:"). To restore the default language mappings for all a par-
ticular language, supply the keyword "default" for the mapping.
To specify restore the default language mappings for all lan-
guages, 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 lan-
guage (either built-in or user-defined) to be used for every sup-
built-in or user-defined). If the first language of list is not
preceded by either a languages in list. Until a '-' is encoun-
tered, 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 lan-
guage or one previously defined with --langdef. The default is
"all", which is also accepted as a valid argument. See TAG KINDS
for a complete list of the built-in language names.
--license
Prints a summary of the software license to standard output.
--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 preproces-
sor 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 gener-
ally only useful when used together with the --excmd=number (-n)
option. Also, you may have to use either the --langmap or --lan-
guage-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 fol-
lowed. When disabled, symbolic links are ignored. This option is
on by default.
--options=file
Read additional options from file.
--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
which to generate tags from source files mapped to the named lan-
guage, <LANG>, (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 spe-
cial 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 cur-
rent 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 kind-spec is expected to be in the form
of a single letter, a comma, and a name followed by a separator,
which specify the short and long forms of the kind value. 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 expres-
sion.
e The pattern is interpreted as a Posix extended regular
expression (default).
i The regular expression is to be applied in a case-insensi-
tive 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 expressionss 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-
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 pro-
cessing 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 con-
figuration 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. This is
guaranteed to always contain the string "Exuberant Ctags".
TAG KINDS
Each type (or kind) of tag recorded in the tag file is indicated by a
one-letter flag, which is also used to filter the tags placed into the
output through use of the --<LANG>-type option. The flags corresponding
to each tag kind for each langauge are described below. 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). Kinds are enabled by default except
where noted (with "[off]").
Asm
d defines
l labels
m macros
t types (structs and records)
ASP
f functions
s subroutines
Awk
f functions
d macro definitions (and #undef names)
e enumerators
f function definitions
g enumeration names
m class, struct, or union members
n namespaces
p function prototypes and declarations [off]
s structure names
t typedefs
u union names
v variable definitions
x extern and forward variable declarations [off]
Cobol
d data items
f file descriptions (FD, SD, RD)
g group items
p paragraphs
P program ids
s sections
Eiffel
c classes
f features
l local entities [off]
Fortran
b block data
c common blocks
e entry points
f functions
i interfaces
k type components
l labels
L local and common block variables [off]
m modules
n namelists
p programs
s subroutines
t derived types
v module variables
Java
c classes
f fields
i interfaces
m methods
p packages
Lisp
f functions
Pascal
f functions
p procedures
Perl
p packages
s subroutines
PHP
c classes
f functions
Python
c classes
f functions
REXX
s subroutines
Ruby
c classes
f functions
m mixins
Scheme
f functions
s sets
Sh (Bourne, Korn, Z)
f functions
SLang
f functions
n namespaces
SQL
c cursors
d prototypes
f functions
F record fields
l local variables
P packages
p procedures
r records
s subtypes
t tables
T triggers
v variables
e enumerator
f function
g enum
m member
p program
P prototype
t task
T typedef
v variable
x externvar
Verilog
f functions
m modules
P parameters
p ports
r registers
t tasks
v variables
w wires
Vim
f functions
YACC
l labels
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 lan-
guage was identified, the file is opened and then the appropriate lan-
guage 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:
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 condi-
tionals, 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 consis-
tency 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 exten-
sion fields (described below) embedded in an EX comment immedi-
ately appended to the EX command, which leaves it backwards
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
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 possi-
ble 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>-types 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 con-
struct 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 cur-
rent 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
HOW TO USE WITH GNU EMACS
Emacs will, by default, expect a tag file by the name "TAGS" in the
current directory. Once the tag file is built, the following commands
exercise the tag indexing feature:
M-x visit-tags-table <RET> FILE <RET>
Select the tag file, "FILE", to use.
M-. [TAG] <RET>
Find the first definition of TAG. The default tag is the
identifier under the cursor.
M-* Pop back to where you previously invoked "M-.".
C-u M-. Find the next definition for the last tag.
For more commands, see the Tags topic in the Emacs info document.
HOW TO USE WITH NEDIT
NEdit version 5.1 and later can handle the new extended tag file format
(see --format). To make NEdit use the tag file, select "File->Load Tags
File". To jump to the definition for a tag, highlight the word, the
press Ctrl-D. NEdit 5.1 can can read multiple tag files from different
directories. Setting the X resource nedit.tagFile to the name of a tag
file instructs NEdit to automatically load that tag file at startup
time.
CAVEATS
Because ctags is neither a preprocessor nor a compiler, use of prepro-
cessor macros can fool ctags into either missing tags or improperly
generating inappropriate tags. Although ctags has been designed to han-
dle 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.
White space is treated as a separator for file names and options read
from list files, specified using the -L option, and in filter mode
(specified using the --filter option). Therefore, it is not currently
possible to supply file names or other options containing embedded
white space (spaces, etc.) through these options.
Note that when ctags generates uses 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 iden-
tical to the line containing the tag. The following example demon-
strates this condition:
int variable;
ter 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::func-
tion"), 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 the function defin-
tion is located in a separate file from than where the class is defined
(the usual case), the access specification (i.e. public, protected, or
private) that the function had when declared in the class is not known.
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 in considered a sep-
arator, making it impossible to pass an option parameter con-
taining an embedded space. If this is a problem, use a configu-
ration 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 tempo-
rary 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
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 quot-
ing is not possible). Each line of the file is read as one com-
mand line parameter (as if it were quoted with single quotes).
Therefore, use new lines to indicate separate command-line argu-
ments.
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@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,