What is the difference between TAB and <tab>?

Question

I was reading the the documentation for Yasnippet mode, when I came to the section where the trigger key is defined:

It seems like Yasnippet minor mode defines the TAB key to run yas-expand using:

(define-key yas-minor-mode-map (kbd "<tab>") 'yas-expand)
(define-key yas-minor-mode-map (kbd "TAB") 'yas-expand)

What is the difference between <tab> and TAB? (I tried to google this but I could not find a clear description)

abo-abo · Accepted Answer · 2015-02-27 09:39:27Z

17

Although Emacs usually translates <tab> (the single key) to TAB (C-i), you can bind <tab> and TAB to different things:

(global-set-key (kbd "<tab>") #'proced)
(global-set-key (kbd "TAB") #'indent-for-tab-command)

answered Feb 27, 2015 at 9:39

abo-abo

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3

I see, but why do Yasnippet need to define both <tab> and TAB?
– Håkon Hægland
Feb 27, 2015 at 9:48
4

@HåkonHægland if you happen to bind them to different commands on the global-map, emacs stops translating one to the other (even on minor mode maps), so yasnippet bind both just in case.
– Malabarba
Feb 27, 2015 at 10:14
1

@Malabarba So if you define both <tab> and TAB, the only way to run the command associated with TAB is to type C-i ?
– Håkon Hægland
Feb 27, 2015 at 10:38
3

If you bind <tab> to a different command than what you bind TAB to, then what you get when you hit the "Tab" key depends on which/what it sends to Emacs. If it sends C-i (aka TAB) then you get the TAB binding. If it sends <tab> then you get its binding. (And yes, you can always hit C-i to get the TAB binding.)
– Drew
Feb 27, 2015 at 15:57
4

More historical information about the different TAB keys are given by StreakyCobra in this spacemacs github issue. You may want to include some of that information in your answer.
– Håkon Hægland
Oct 28, 2016 at 9:16

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