changing tags-file-name

changing tags-file-name

[James K. Lowden]

I decided to broaden a tags search by scanning from a higher point in
the source tree.  So I want to tell xref to use a different file.  But
set-variable says there's no such variable: 


The name of the file AIUI is tags-file-name, which C-h v describes as: 

tags-file-name is a variable defined in ?etags.el?.
Its value is
"/home/jklowden/projects/3rd/libdwarf/code/dwarfgen/TAGS"

  This variable is safe as a file local variable if its value
  satisfies the predicate ?stringp?.

Documentation:
File name of tags table.
To switch to a new tags table, setting this variable is sufficient.
[...]

When I use M-x set-variable, it rejects tags-file-name.  For
"tags-" completion it says, 

Possible completions are:
tags-add-tables 	tags-apropos-additional-actions
tags-apropos-verbose 	tags-case-fold-search
tags-compression-info-list 	tags-loop-revert-buffers
tags-revert-without-query 	tags-table-list
tags-tag-face

Why would emacs display a variable name, document that setting is
fine, and not be able to set it?  

Is there an easier way to change the tags file name (or add one and
drop one) that I'm overlooking? 

Thanks.  

--jkl


--jkl

Re: changing tags-file-name

[Eli Zaretskii]

> From: "James K. Lowden" <jklowden@speakeasy.net>
> Date: Tue, 5 Dec 2017 11:31:56 -0500
> 
> The name of the file AIUI is tags-file-name, which C-h v describes as: 
> 
> tags-file-name is a variable defined in ?etags.el?.
> Its value is
> "/home/jklowden/projects/3rd/libdwarf/code/dwarfgen/TAGS"
> 
>   This variable is safe as a file local variable if its value
>   satisfies the predicate ?stringp?.
> 
> Documentation:
> File name of tags table.
> To switch to a new tags table, setting this variable is sufficient.
> [...]
> 
> When I use M-x set-variable, it rejects tags-file-name.  For
> "tags-" completion it says, 
> 
> Possible completions are:
> tags-add-tables 	tags-apropos-additional-actions
> tags-apropos-verbose 	tags-case-fold-search
> tags-compression-info-list 	tags-loop-revert-buffers
> tags-revert-without-query 	tags-table-list
> tags-tag-face
> 
> Why would emacs display a variable name, document that setting is
> fine, and not be able to set it?  

set-variable only supports user options (a.k.a. "defcustoms").  For
other variables, use

  M-: (setq VAR VALUE) RET

> Is there an easier way to change the tags file name (or add one and
> drop one) that I'm overlooking? 

You are overlooking "M-x visit-tags-table RET", I think.

Re: changing tags-file-name

[James K. Lowden]

On Fri, 08 Dec 2017 12:35:05 +0200
Eli Zaretskii <eliz@gnu.org> wrote:

> > Why would emacs display a variable name, document that setting is
> > fine, and not be able to set it?  
> 
> set-variable only supports user options (a.k.a. "defcustoms").  For
> other variables, use
> 
>   M-: (setq VAR VALUE) RET

Thanks.  Your explanation helped me understand the documentation for
set-variable.  

> > Is there an easier way to change the tags file name (or add one and
> > drop one) that I'm overlooking? 
> 
> You are overlooking "M-x visit-tags-table RET", I think.

Yes, indeed.  "apropos tags" does mention that, but I missed it.  

Many thanks, Eli!    

--jkl