Home » Linux Command Reference » UNIX/LINUX Command – etags

UNIX/LINUX Command – etags

Last updated May 10, 2021


etags—Generate tag file for emacs
ctags—Generate tag file for vi


etags [ –aCDSVH] [ –i file ][–o tagfile ] [ –c++ ] [ –no–defines] [ –ignore–indentation ] [ –help ] [ –version ] [ –include=file ] [ –output=tagfile ] [ –append ] file …

ctags [ –aCdSVH] [ –BtTuvwx ] [ –o tagfile ] [ –c++ ] [ –defines ] [ –ignore–indentation ] [ –backward–search] [ –forward–search ] [ –typedefs ] [ –typedefs–and–c++] [ –no–warn ] [ –cxref ] [ –help ] [ –version ] [ –output=tagfile ] [ –append ] [ –update ] file …


The etags program is used to create a tag table file, in a format understood by emacs(1); the ctags program is used to create a similar table in a format understood by vi(1) . Both forms of the program understand the syntax of C, FORTRAN, Pascal, LaTeX, cheme, emacs Lisp/Common Lisp, and most assembler–like syntaxes. Both forms read the files specified on the command line, and write a tag table (defaults: TAGS for etags, tags for ctags) in the current working directory.

The programs recognize the language used in an input file based on its filename and contents; there are no switches for specifying the language.


Some options make sense only for the vi-style tag files produced by ctags; etags does not recognize them. The programs accept unambiguous abbreviations for long option names.

Options Description
–a, –append Append to existing tag file. (For vi-format tag files, see also –update.)
–B, –backward–search Tag files written in the format expected by vi contain regular expression search instructions; the –B option writes them using the delimiter ?, to search backwards through files. The default is to use the delimiter / to search forwards through files. Only ctags accepts this option.
–C, –c++ Treat files with .c and .h extensions as C++ code, not C code. Files with .C, .H, .cxx, .hxx, or .cc extensions are always assumed to be C++ code.
–d, –defines Create tag entries for C preprocessor definitions, too. This is the default behavior for etags, so this option is only accepted by ctags.
–D, –no–defines Do not create tag entries for C preprocessor definitions. This may make the tags file much smaller if many header files are tagged. This is the default behavior for ctags, so this option is only accepted by etags.
-i file, –include=file Include a note in tag file indicating that, when searching for a tag, one should also consult the tags file file after checking the current file. Only etags accepts this option.
–o tagfile, –output=tagfile Explicit name of file for tag table; overrides default TAGS or tags. (But ignored with –v or –x.)
–S, –ignore–indentation Don’t rely on indentation as much as we normally do. Currently, this means not to assume that a closing brace in the first column is the final brace of a function or structure definition in C and C++.
–t, –typedefs Record typedefs in C code as tags. Since this is the default behavior of etags, only ctags accepts this option.
–T, –typedefs–and–c++ Generate tag entries for typedefs, struct, enum, and union tags, and C++ member functions. Since this is the default behavior of etags, only ctags accepts this option.
–u, –update Update tag entries for files specified on command line, leaving tag entries for other files in place. Currently, this is implemented by deleting the existing entries for the given files and then rewriting the new entries at the end of the tags file. It is often faster to simply rebuild the entire tag file than to use this. Only ctags accepts this option.
–v, —vgrind Instead of generating a tag file, write index (in vgrind format) to standard output. Only ctags accepts this option.
–w, –no–warn Suppress warning messages about duplicate entries. The etags program does not check for duplicate entries, so this option is not allowed with it.
–x, —cxref Instead of generating a tag file, write a cross-reference (in cxref format) to standard output. Only ctags accepts this option.
–H, –help Print usage information.
–V, –version Print the current version of the program (same as the version of the emacs etags is shipped with).

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