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GTAGS(1) General Commands Manual GTAGS(1)


gtags - create tag files for global


gtags [-ciIOqvw][-d tag-file][-f file][dbpath]


Gtags is used to create tag files for global(1).

Gtags recursively collects source files under the current directory, picks up symbols and writes the cross-reference data into the tag files (´GTAGS´, ´GRTAGS´ and ´GPATH´).

If ´gtags.files´ exists in the current directory or a file is specified by the -f option, target files are limited by it. Lines starting with ´. ´ are comments.

C, yacc, Assembly, Java, C++ and PHP source files are supported. Files whose names end in ´.c´, ´.h´ are assumed to be C source files. Files whose names end in ´.y´ are assumed to be yacc source files. Files whose names end in ´.s´, ´.S´ are assumed to be Assembly source files. Files whose names end in ´.java´ are assumed to be Java source files. Files whose names end in ´.c++´, ´.cc´, ´.hh´, ´.cpp´, ´.cxx´, ´.hxx´, ´.hpp´, ´.C´, ´.H´ are assumed to be C++ source files. Files whose names end in ´.php´, ´.php3´, ´.phtml´ are assumed to be PHP source files. Other files are assumed to be text files. Gtags does not treat binary files.


The following options are available:
Accept files and directories whose names begin with a dot. By default, gtags ignores them.
-c, --compact
Make ´GTAGS´ in compact format. This option does not influence ´GRTAGS´, because that is always made in compact format.
Print the value of config variable name. If name is not specified then print all names and values. In addition to the variables listed in the ENVIRONMENT section, you can refer to install directories by read only variables: bindir, libdir, datadir, localstatedir and sysconfdir.
-d, --dump tag-file
Dump a tag file as text to the standard output. Output format is ´key<tab>data'. This is for debugging.
Explain handling files.
-f, --file file
Give a list of candidates of target files. Files which are not on the list are ignored. The argument file can be set to ´-´ to accept a list of files from the standard input. File names must be separated by newline. To make the list, you may use find(1) which has rich options for selecting files.
--gtagsconf file
Set environment variable GTAGSCONF to file.
--gtagslabel label
Set environment variable GTAGSLABEL to label.
-I, --idutils
In addition to tag files, make ID database for idutils(1).
-i, --incremental
Update tag files incrementally. It's better to use global(1) with the -u command.
-O, --objdir
Use BSD-style objdir as the location of tag files. If ´$MAKEOBJDIRPREFIX´ directory exists, gtags creates ´$MAKEOBJDIRPREFIX/<current directory>´ directory and makes tag files in it. If dbpath is specified, this option is ignored.
--single-update file
Update tag files for a single file. It is considered that file was added, updated or deleted, and there is no change in other files. This option implies the -i option.
Skip unreadable files.
Use Sqlite 3 API to make tag files. By default, BSD/DB 1.85 API is used. To use this option, you need to invoke configure script with --with-sqlite3 in the build phase.
Print statistics information.
-q, --quiet
Quiet mode.
-v, --verbose
Verbose mode.
-w, --warning
Print warning messages.
The directory in which tag files are generated. The default is the current directory.


$ ls -F
Makefile      src/    lib/
$ gtags -v
$ global -x main
main              10 src/main.c  main (argc, argv) {


Tag file for definitions.
Tag file for references.
Tag file for source files.
´gtags.conf´, ´$HOME/.globalrc´
See gtags.conf(5).
The list of candidates of target files.


The following environment variables affect the execution of gtags:
The size of the B-tree cache. The default is 50000000 (bytes).
Configuration file.
If this variable is set, each file whose suffix is ´.h´ is treated as a C++ source file.
If this variable is set, each } at the first column brings end of block of 0 level.
Configuration label. The default is ´default´.
If this variable is set, ´$GTAGSLOGGING´ is used as the path name of a log file. There is no default value.
This variable can only be referenced from the hook (See gtags_hook). Gtags set its own effective command line to this variable before calling the hook. Each argument is sepalated by whitespace, and real whitespace is represented as '%20'. This is read only.
The value of this variable is inserted in the head of arguments.
If this variable is set, ´$MAKEOBJDIR´ is used as the name of BSD-style objdir. The default is ´obj´.
If this variable is set, ´$MAKEOBJDIRPREFIX´ is used as the prefix of BSD-style objdir. The default is ´/usr/obj´.
The location used to stored temporary files. The default is ´/tmp´.


The following configuration variables affect the execution of gtags. You can see the default value for each variable with the --config option.
gtags_parser (comma separated list)
Specify the mapping of language names and plug-in parsers. Each part delimited by the comma consists of the language name, a colon, the shared object path, an optional colon followed by a function name. If the function name is not specified, 'parser' is assumed. As a special exception, gtags collects values from multiple gtags_parser variables.
gtags_hook (command line)
Specify a command line which should be executed at the beginning of gtags after loading configuration file. You can use this hook to update ´gtags.files´ dynamically.. "./" in it always means the project root directory, since gtags is always invoked there.
icase_path (boolean)
Ignore case distinctions in the path. Suffixes check is affected by this capability.
langmap (comma separated list)
Language mapping. Each comma-separated map consists of the language name, a colon, and a list of file extensions. As a special exception, gtags collects values from multiple langmap variables. Default mapping is:
skip (comma separated list)
Gtags skips files and directories which are given in this list. As a special exception, gtags collects values from multiple skip variables. If the value ends with ´/´, it is assumed as a directory and gtags skips all files under it. The value may include glob patterns (*, ?, [...], [!...], [^...]).

If the value starts with ´/´, it is assumed a relative path name from the root directory of the project. You cannot use glob patterns for a path name. However, this directions is out-of-date, and is not recommended. Instead, you can use -f option which can be combined with find(1). Since find(1) has rich options to select files, you can do everything. Additionally, this technique can also be applied to any other tagging systems like ctags(1), cscope(1), and etc.

Skip list is also effective when you use the -f or ´gtags.files´.


Gtags exits with a non-0 value if an error occurred, 0 otherwise.

Note that files created by gtags with a non-zero exit code should be considered corrupted.


global(1), htags(1), gtags.conf(5).

GNU GLOBAL source code tag system


´GTAGS´ and ´GRTAGS´ are very large. In advance of using this command, check the space of your disk.

Assembly support is far from complete. It extracts only ENTRY() and ALTENTRY() from source file. Probably valid only for FreeBSD and Linux kernel source.

There is no concurrency control about tag files.


Shigio YAMAGUCHI, Hideki IWAMOTO and others.


The gtags command appeared in FreeBSD 2.2.2.
September 2016 GNU Project