PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

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

NAME         top

       ctags — create a tags file (DEVELOPMENT, FORTRAN)

SYNOPSIS         top

       ctags [−a] [−f tagsfile] pathname...

       ctags −x pathname...

DESCRIPTION         top

       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         top

       The ctags utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, 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         top

       The following pathname operands are supported:

       file.c    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.h    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.f    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         top

       See the INPUT FILES section.

INPUT FILES         top

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

ENVIRONMENT VARIABLES         top

       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.1‐2008, 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         top

       Default.

STDOUT         top

       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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       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         top

       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 M to the name of the file, with the trailing .c, 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         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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
       #defines, 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         top

       None.

RATIONALE         top

       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 typedefs 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.1‐2008 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.1‐2008:

       −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         top

       None.

SEE ALSO         top

       c99(1p), fort77(1p), vi(1p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                           CTAGS(1P)