CTAGS(1)                   POSIX Programmer's Manual                  CTAGS(1)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       ctags -- create a tags file (DEVELOPMENT, FORTRAN)

SYNOPSIS
       ctags [[-a]] [[-f tagsfile]] pathname...

       ctags -x pathname...

DESCRIPTION
       The ctags utility shall be provided on systems that support the the
       Software Development Utilities option, and either or both of the C-
       Language Development Utilities option and FORTRAN Development Utilities
       option. On other systems, it is optional.

       The ctags utility shall write a tagsfile or an index of objects from C-
       language or FORTRAN source files specified by the pathname operands.
       The tagsfile shall list the locators of language-specific objects
       within the source files. A locator consists of a name, pathname, and
       either a search pattern or a line number that can be used in searching
       for the object definition. The objects that shall be recognized are
       specified in the EXTENDED DESCRIPTION section.

OPTIONS
       The ctags utility shall conform to the Base Definitions volume of
       POSIX.1-2017, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -a        Append to tagsfile.

       -f tagsfile
                 Write the object locator lists into tagsfile instead of the
                 default file named tags in the current directory.

       -x        Produce a list of object names, the line number, and filename
                 in which each is defined, as well as the text of that line,
                 and write this to the standard output. A tagsfile shall not
                 be created when -x is specified.

OPERANDS
       The following pathname operands are supported:

       file..cc    Files with basenames ending with the .c suffix shall be
                 treated as C-language source code. Such files that are not
                 valid input to c99 produce unspecified results.

       file..hh    Files with basenames ending with the .h suffix shall be
                 treated as C-language source code. Such files that are not
                 valid input to c99 produce unspecified results.

       file..ff    Files with basenames ending with the .f suffix shall be
                 treated as FORTRAN-language source code. Such files that are
                 not valid input to fort77 produce unspecified results.

       The handling of other files is implementation-defined.

STDIN
       See the INPUT FILES section.

INPUT FILES
       The input files shall be text files containing source code in the
       language indicated by the operand filename suffixes.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of
       ctags:

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1-2017, Section 8.2, Internationalization
                 Variables for the precedence of internationalization
                 variables used to determine the values of locale categories.)

       LC__ALL    If set to a non-empty string value, override the values of
                 all the other internationalization variables.

       LC__COLLATE
                 Determine the order in which output is sorted for the -x
                 option. The POSIX locale determines the order in which the
                 tagsfile is written.

       LC__CTYPE  Determine the locale for the interpretation of sequences of
                 bytes of text data as characters (for example, single-byte as
                 opposed to multi-byte characters in arguments and input
                 files). When processing C-language source code, if the locale
                 is not compatible with the C locale described by the ISO C
                 standard, the results are unspecified.

       LC__MESSAGES
                 Determine the locale that should be used to affect the format
                 and contents of diagnostic messages written to standard
                 error.

       NLSPATH   Determine the location of message catalogs for the processing
                 of LC__MESSAGES.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The list of object name information produced by the -x option shall be
       written to standard output in the following format:


           "%s %d %s %s", <object-name>, <line-number>, <filename>, <text>

       where <text> is the text of line <line-number> of file <filename>.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       When the -x option is not specified, the format of the output file
       shall be:


           "%s\t%s\t/%s/\n", <identifier>, <filename>, <pattern>

       where <pattern> is a search pattern that could be used by an editor to
       find the defining instance of <identifier> in <filename> (where
       defining instance is indicated by the declarations listed in the
       EXTENDED DESCRIPTION).

       An optional <circumflex> (''^^'') can be added as a prefix to <pattern>,
       and an optional <dollar-sign> can be appended to <pattern> to indicate
       that the pattern is anchored to the beginning (end) of a line of text.
       Any <slash> or <backslash> characters in <pattern> shall be preceded by
       a <backslash> character. The anchoring <circumflex>, <dollar-sign>, and
       escaping <backslash> characters shall not be considered part of the
       search pattern. All other characters in the search pattern shall be
       considered literal characters.

       An alternative format is:


           "%s\t%s\t?%s?\n", <identifier>, <filename>, <pattern>

       which is identical to the first format except that <slash> characters
       in <pattern> shall not be preceded by escaping <backslash> characters,
       and <question-mark> characters in <pattern> shall be preceded by
       <backslash> characters.

       A second alternative format is:


           "%s\t%s\t%d\n", <identifier>, <filename>, <lineno>

       where <lineno> is a decimal line number that could be used by an editor
       to find <identifier> in <filename>.

       Neither alternative format shall be produced by ctags when it is used
       as described by POSIX.1-2008, but the standard utilities that process
       tags files shall be able to process those formats as well as the first
       format.

       In any of these formats, the file shall be sorted by identifier, based
       on the collation sequence in the POSIX locale.

EXTENDED DESCRIPTION
       If the operand identifies C-language source, the ctags utility shall
       attempt to produce an output line for each of the following objects:

        *  Function definitions

        *  Type definitions

        *  Macros with arguments

       It may also produce output for any of the following objects:

        *  Function prototypes

        *  Structures

        *  Unions

        *  Global variable definitions

        *  Enumeration types

        *  Macros without arguments

        *  #define statements

        *  #line statements

       Any #if and #ifdef statements shall produce no output. The tag main is
       treated specially in C programs. The tag formed shall be created by
       prefixing MM to the name of the file, with the trailing ..cc, and leading
       pathname components (if any) removed.

       On systems that do not support the C-Language Development Utilities
       option, ctags produces unspecified results for C-language source code
       files. It should write to standard error a message identifying this
       condition and cause a non-zero exit status to be produced.

       If the operand identifies FORTRAN source, the ctags utility shall
       produce an output line for each function definition. It may also
       produce output for any of the following objects:

        *  Subroutine definitions

        *  COMMON statements

        *  PARAMETER statements

        *  DATA and BLOCK DATA statements

        *  Statement numbers

       On systems that do not support the FORTRAN Development Utilities
       option, ctags produces unspecified results for FORTRAN source code
       files. It should write to standard error a message identifying this
       condition and cause a non-zero exit status to be produced.

       It is implementation-defined what other objects (including duplicate
       identifiers) produce output.

EXIT STATUS
       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The output with -x is meant to be a simple index that can be written
       out as an off-line readable function index. If the input files to ctags
       (such as .c files) were not created using the same locale as that in
       effect when ctags -x is run, results might not be as expected.

       The description of C-language processing says ``attempts to'' because
       the C language can be greatly confused, especially through the use of
       ##ddeeffiinnees, and this utility would be of no use if the real C
       preprocessor were run to identify them. The output from ctags may be
       fooled and incorrect for various constructs.

EXAMPLES
       None.

RATIONALE
       The option list was significantly reduced from that provided by
       historical implementations. The -F option was omitted as redundant,
       since it is the default. The -B option was omitted as being of very
       limited usefulness. The -t option was omitted since the recognition of
       ttyyppeeddeeffs is now required for C source files. The -u option was omitted
       because the update function was judged to be not only inefficient, but
       also rarely needed.

       An early proposal included a -w option to suppress warning diagnostics.
       Since the types of such diagnostics could not be described, the option
       was omitted as being not useful.

       The text for LC__CTYPE about compatibility with the C locale
       acknowledges that the ISO C standard imposes requirements on the locale
       used to process C source. This could easily be a superset of that known
       as ``the C locale'' by way of implementation extensions, or one of a
       few alternative locales for systems supporting different codesets. No
       statement is made for FORTRAN because the ANSI X3.9-1978 standard
       (FORTRAN 77) does not (yet) define a similar locale concept. However, a
       general rule in this volume of POSIX.1-2017 is that any time that
       locales do not match (preparing a file for one locale and processing it
       in another), the results are suspect.

       The collation sequence of the tags file is not affected by LC__COLLATE
       because it is typically not used by human readers, but only by programs
       such as vi to locate the tag within the source files. Using the POSIX
       locale eliminates some of the problems of coordinating locales between
       the ctags file creator and the vi file reader.

       Historically, the tags file has been used only by ex and vi.  However,
       the format of the tags file has been published to encourage other
       programs to use the tags in new ways. The format allows either patterns
       or line numbers to find the identifiers because the historical vi
       recognizes either. The ctags utility does not produce the format using
       line numbers because it is not useful following any source file changes
       that add or delete lines.  The documented search patterns match
       historical practice. It should be noted that literal leading
       <circumflex> or trailing <dollar-sign> characters in the search pattern
       will only behave correctly if anchored to the beginning of the line or
       end of the line by an additional <circumflex> or <dollar-sign>
       character.

       Historical implementations also understand the objects used by the
       languages Pascal and sometimes LISP, and they understand the C source
       output by lex and yacc.  The ctags utility is not required to
       accommodate these languages, although implementors are encouraged to do
       so.

       The following historical option was not specified, as vgrind is not
       included in this volume of POSIX.1-2017:

       -v        If the -v flag is given, an index of the form expected by
                 vgrind is produced on the standard output. This listing
                 contains the function name, filename, and page number
                 (assuming 64-line pages). Since the output is sorted into
                 lexicographic order, it may be desired to run the output
                 through sort -f.  Sample use:


                     ctags -v files | sort -f > index vgrind -x index

       The special treatment of the tag main makes the use of ctags practical
       in directories with more than one program.

FUTURE DIRECTIONS
       None.

SEE ALSO
       c99, fort77, vi

       The Base Definitions volume of POSIX.1-2017, Chapter _8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             CTAGS(1)
