ctags(1)

NAME

ctags — create a tags file

SYNOPSIS

ctags [-xvFBatwu] files ...

DESCRIPTION

ctags makes a tags file for ex(1) (or vi(1)) from the specified C, Pascal and FORTRAN sources. A tags file gives the locations of specified objects (for C, functions, macros with argments, and typedefs; Pascal, procedures, programs and functions; FORTRAN, subroutines, programs and functions) in a group of files. Each line of the tags file contains the object name, the file in which it is defined, and an address specification for the object definition. Output is sorted in ascending collation order (see Environment Variables below). All objects except C typedefs are searched with a pattern, typedefs with a line number. Specifiers are given in separate fields on the line, separated by spaces or tabs. Using the tags file, ex can quickly find these objects' definitions.

-x: Cause ctags to print a simple function index. This is done by assembling a list of function names, file names on which each function is defined, the line numbers where each function name occurs, and the text of each line. The list is then printed on the standard output. No tags file is created or changed.
-v: Produce a page index on the standard output. This listing contains the function name, file name, and page number within that file (assuming 56-line pages to match pr(1)).

Files whose name ends in .c or .h are assumed to be C source files and are searched for C routine and macro definitions. Others are first examined to see if they contain any Pascal or FORTRAN routine definitions; if not, they are processed again looking for C definitions.

Other options are:

-F: Use forward searching patterns (/.../) (default).
-B: Use backward searching patterns (?...?).
-a: Add the information from the files to the tags file. Unlike re-building the tags file from the original files, this can cause the same symbol to be entered twice in the tags file. This option should be used with caution and then only in very special circumstances.
-t: Create tags for typedefs.
-w: Suppress warning diagnostics.
-u: Update the specified files in tags; that is, all references to those files are deleted, and the new values are added to the file as in -a above. (Beware: this option is implemented in a way which is rather slow; it is usually faster to simply rebuild the tags file.)

The tag main is treated specially in C programs. The tag formed is created by adding M to the beginning of name of the file, with any trailing .c removed, and leading pathname components also removed. This makes use of ctags practical in directories with more than one program.

EXTERNAL INFLUENCES

Environment Variables

LC_COLLATE determines the order in which the output is sorted.

LC_CTYPE determines the interpretation of the single- and/or multi-byte characters within comments and string literals.

If LC_COLLATE or LC_CTYPE is not specified in the environment or is set to the empty string, the value of LANG is used as a default for each unspecified or empty variable. If LANG is not specified or is set to the empty string, a default of ``C'' (see lang(5)) is used instead of LANG. If any internationalization variable contains an invalid setting, ctags behaves as if all internationalization variables are set to ``C''. See environ(5).

International Code Set Support

Single- and multi-byte character code sets are supported with the exception that multi-byte character file names are not supported.

DIAGNOSTICS

Too many entries to sort.

An attempt to get additional heap space failed; the sort could not be performed.

Unexpected end of function in file file, line line.

The tags file may be incorrect.

A } character was found unexpectedly in the first column. This can lead to incorrect entries in the tags file.

Duplicate entry in file file, line line: name. Second entry ignored.

The same name was detected twice in the same file. A tags entry was made only for the first name found.

Duplicate entry in files file1 and file2: name (Warning only).

The same name was detected in two different files. A tags entry was made only for the first name found.

EXAMPLES

Create a tags file named tags in the current directory for all C source (*.c) files and all header (*.h) files in the current directory:

ctags *.[ch] 

Once the tags file exists in the current directory, it can be used with commands that support tag files (such as vi (see vi(1)).

Use the tags file with vi to edit a particular function myfunc() located in one of the source files:

vi -t myfunc 

While editing a C source file using vi, use the ex-mode tag command to edit function myfunc():

:tag myfunc 

Use vi to find main() in file myprog.c:

vi -t Mmyprog 

While using vi, find main() in file myprog.c (does not have to be the file currently being edited):

:tag Mmyprog 

WARNINGS

Recognition of functions, subroutines, and procedures for FORTRAN and Pascal is done in a very simple way. No attempt is made to deal with block structure; if there are two Pascal procedures in different blocks with the same name, a warning message is generated.

The method of deciding whether to look for C or Pascal and FORTRAN functions is an approximation, and can be fooled by unusual programs.

ctags does not know about #ifdefs and Pascal types.

It relies on the input being well formed to detect typedefs.

Use of -tx shows only the last line of typedefs.

ex is naive about tags files with several identical tags; it simply chooses the first entry its (non-linear) search finds with that tag. Such files can be created with either the -u or -a options or by editing a tags file.

If more than one (function) definition appears on a single line, only the first definition is indexed.

AUTHOR

ctags was developed by the University of California, Berkeley.

FILES

tags: output tags file
OTAGS: temporary file used by -u

STANDARDS CONFORMANCE

ctags: XPG4