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Add info about Backspace and Delete to the FAQ
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FAQ
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FAQ
@ -98,3 +98,61 @@ If you want to compile st for OpenBSD you have to remove -lrt from config.mk, an
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st will compile without any loss of functionality, because all the functions are
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included in libc on this platform.
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## Backspace key does not work
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This is an issue that was discussed in suckless mailing list
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<http://lists.suckless.org/dev/1404/20697.html>:
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Well, I am going to comment why I want to change the behaviour
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of this key. When ascii was defined in 1968 communication
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with computers were done using punched cards, or hardcopy
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terminals (basically a typewritter machine connected with
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the computer using a serial port). Due to this, ascii defines
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DELETE as 7F, because in the puched cards, it means all the
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holes of the card punched, so it is a kind of 'phisical
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delete'. In the same way, BACKSPACE key was a non destructive
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back space, as in typewriter machines. So, if you wanted
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to delete a character, you had to BACKSPACE and then DELETE.
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Other use of BACKSPACE was accented characters, for example
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'a BACKSPACE `'. The VT100 had no BACKSPACE key, it was
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generated using the CONTROL key as another control character
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(CONTROL key sets to 0 b7 b6 b5, so it converts H (code
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0x48) into BACKSPACE (code 0x08)), but it had a DELETE key
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in a similar position where BACKSPACE key is located today
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in common PC keyboards. All the terminal emulators emulated
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correctly the difference between these keys, and backspace
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key generated a BACKSPACE (^H) and delete key generated a
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DELETE (^?).
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But the problem arised when Linus Torvald wrote Linux, and
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he did that the virtual terminal (the terminal emulator
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integrated in the kernel) returns a DELETE when backspace
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was pressed, due to the fact of the key in that position
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in VT100 was a delete key. This created a lot of problems
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(you can see it in [1] and [2]), and how Linux became the
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king, a lot of terminal emulators today generate a DELETE
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when backspace key is pressed in order to avoid problems
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with linux. It causes that the only way of generating a
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BACKSPACE in these systems is using CONTROL + H. I also
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think that emacs had an important point here because CONTROL
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+ H prefix is used in emacs in some commands (help commands).
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From point of view of the kernel, you can change the key
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for deleting a previous character with stty erase. When you
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connect a real terminal into a machine you describe the
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type of terminal, so getty configure the correct value of
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stty erase for this terminal, but in the case of terminal
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emulators you don't have any getty that can set the correct
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value of stty erase, so you always get the default value.
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So it means that in case of changing the value of the
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backspace keyboard, you have to add a 'stty erase ^H' into
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your profile. Of course, other solution can be that st
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itself modify the value of stty erase. I have usually the
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inverse problem, when I connect with non Unix machines, and
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I have to press control + h to get a BACKSPACE, or the
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inverse, when a user connects to my unix machines from a
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different system with a correct backspace key.
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[1] http://www.ibb.net/~anne/keyboard.html
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[2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html
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