Man page of CTAGS
Section: User Commands (1)
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ctags - Generates "tags" and (optionally) "refs" files
This page describes the
files from a group of C source files.
file is used by Elvis' ":tag" command,
^] command, and -t option.
file is sometimes used by the
Each C source file is scanned for #define statements and
global function definitions.
The name of the macro or function becomes the name of a tag.
For each tag, a line is added to the
The filenames list will typically be the names of all C source
files in the current directory, like this:
$ ctags *.c *.h
If no options are given, then
acts as though the
-l -i -t -v
option flags were given.
If you want to omit those options, you can do so by explicitly giving
a harmless option such as
This causes Elvis to ignore any instance of "word" in your source code.
This is handy if you're using a macro for conditionally declaring the arguments
to functions, in order to make your code be backward-compatible with older K&R
ctags always ignores "P_" and "__P";
the -Dword flag allows you to make it ignore a third word.
Enclose regular expressions in slashes (/regexp/) which will cause
to search from the top of the file.
This is the default.
Enclose the regular expressions in question marks (?regexp?) so
will search backward from the bottom of the file.
The search direction rarely matters; this option exists mostly for
compatibility with earlier versions of ctags.
to use line numbers for all tags.
Without this flag, it would use numbers for #define'ed macros,
and regular expressions for anything else.
For static tags, generate entries that look like global tags.
(I.e., never generate an extra "file:" attribute.)
This implies -s and -h.
Include inline definitions.
A tag will be generated for each function which is declared as being
inline, __inline, or __inline__.
A tag will be generated for each user-defined type.
Also tags will be generated for struct and enum names.
Types are considered to be global if they are defined in a header file,
and static if they are defined in a C source file.
Include variable declarations.
A tag will be generated for each variable, except for those that are declared
inside the body of a function.
Include static tags.
will normally put global tags in the
file, and silently ignore the static tags.
This flag causes both global and static tags to be added.
Include extern tags.
will normally ignore extern declarations of functions or variables;
that's handy when generating tags for your own programs.
A tags file for the extern declarations in the system's standard header files
can be a very handy resource, so this -e flag was created.
Add hints that may help Elvis handle overloaded tags better.
The resulting tags file may be unreadable by programs other than Elvis, though.
Add "ln" line number hints.
This implies -h, since it would be pointless if hints weren't allowed.
The "ln" hints are used by
to make its "showtag" option work much faster.
Write parsing information to stdout.
This is intended mainly as an aid to debugging the ctags command itself.
If ctags doesn't generate all of the tags that you expect it to,
then try studying the -p output to determine what syntax feature is
tripping it up.
Warn about duplicates, on stdout.
allows tags with duplicate names, except for typedefs (tags with kind=t)
which must be unique.
When a duplicate tag is detected,
can either add it if neither the new tag nor the existing one has "kind=t",
skip it if the existing one has "kind=t", or
add it and delete the existing one if the new one has "kind=t".
Usually you won't care, but
may help you understand why
fails to add a tag that you expected it to add.
Generate a human-readable tag list instead of a "tags" file.
The list is written to stdout.
Each line contains a tag name, the line number and file name where
the tag is defined, and the text of that line.
to generate both
Without -r, it would only generate
overwrites these files each time it is invoked.
This flag is useful when you have too many files in the current directory
for you to list them on a single command-line;
it allows you to split the arguments among several invocations.
This may result in an unsorted tags file.
FORMAT OF THE TAGS FILE
file is a text file.
Each line stores the attributes of a single tag.
The basic format of a line is:
* the name of the tag
* a tab character
* the name of the file containing the tag
* a tab character
* the tag's address within that file
The tag address may be given as either line number (a string of digits),
or a regular expression using ex/vi's "nomagic" syntax, delimited by either
slashes or question marks.
Regular expressions are allowed to contain tab characters.
The authors of Elvis, Vim, and "Exuberant" Ctags have agreed on a
standard format for adding additional attributes to tags.
In this format, the first three fields of all tags are identical to the
traditional format, except that a semicolon-doublequote character pair
is appended to the tag address field, with the extra attributes appearing
The semicolon-doublequote character pair is present because it has the
surprising side-effect of making the original ex/vi ignore the remainder
of the line, thus allowing the original ex/vi to read new-format tags files.
The original ex/vi will simply ignore the extra attributes.
Any additional attributes are appended to the tag's line.
They may be appended in any order.
Each attribute will use the following format:
* a tab character
* the name of the attribute
* a colon character, ':'
* the value of the attribute.
Note that each additional attribute has an explicit name.
Different tags files may use totally different names for additional attributes,
and even within a single file, most tags will use only a subset of the
This version of ctags uses the following names:
This attribute is used to mark static tags -- i.e., tags for C/C++ functions
or variables whose scope is limited to the function in which they are
The value is the name of the file where it is defined,
except that if the file is the same as field 2
(and it nearly always is)
then the value may be given as a zero-length string.
This is used to mark member functions of C++ classes.
The value is the class name.
However, currently ctags doesn't do a very good job of detecting whether a
function is a member function or not.
This attribute's value is a single letter, indicating the lexical type
of the tagged identifier:
f for a function,
t for a typedef,
s for a struct tag,
u for a union tag,
v for a variable,
d for a macro definition, or
x for an extern declaration.
Note that in the tags file, the "kind:" label is omitted, for the sake of compactness.
This gives the line number where the tag was defined.
It is redundant, but it is still somewhat useful because it allows
"showtag" option to work faster.
The values can only contain tabs if those tabs are converted to the '\t'
Similarly, a newline, carriage return, or literal backslash can be given
as '\n', '\r', or '\\' respectively.
For MS-DOS file names, this means the names must use double backslashes.
Space characters don't require any special encoding.
(This doesn't apply to file names in the
field, where names can be given without any special encoding.
It only applies to file names in extra fields.)
As a special case, if an extra attribute contains no ':' to delimit the
name from the value, then the attribute string is assumed to be the value
of an attribute named "kind".
Usually this will be a single letter indicating what type of token the
tag represents -- 'f' for function, 'v' for variable, and so on.
Here's an example of a new-format tag:
The tagname is "bar", to match its function's name.
The tagfile is "foo.c".
The tagaddress is a regular expression containing the whole definition line.
Note that a semicolon-doublequote character pair has been appended to the
There is only one additional attribute, with the name "class" and the value
bar foo.c /^void Foo::bar(int zot)$/;" class:Foo
A cross-reference that lists each tag name, the name of the source file that
contains it, and a way to locate a particular line in the source file.
file contains the definitions for each tag in the
file, and very little else.
This file can be useful, for example, when licensing restrictions prevent
you from making the source code to the standard C library readable by everybody,
but you still want everybody to know what arguments the library functions need.
is sensitive to indenting and line breaks.
Consequently, it might not discover all of the tags in a file that
is formatted in an unusual way.
flag causes tag files to be appended, but not necessarily sorted.
Some programs expect tags files to be sorted, and will misbehave if they
Also, the new format allows a "!_TAG_FILE_SORTED" marker near the top of the
file to indicate whether the file is sorted, but that might not be accurate
after new tags are appended to the file.
Consequently, you should avoid the use of
The new standard doesn't specify how overloaded operators are to be labelled.
If your C++ source contains a definition of operator+=(), then this version of
will store a tag named "operator+=".
Other versions of ctags could simply use the name "+=".
- FORMAT OF THE TAGS FILE
- SEE ALSO
This document was created by
using the manual pages.
Time: 11:33:37 GMT, October 24, 2003