--- FAQ | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+)
diff --git a/FAQ b/FAQ index f8a2ec2..a0f947c 100644 --- a/FAQ +++ b/FAQ @@ -98,3 +98,61 @@ If you want compile st for OpenBSD you have to remove -lrt from config.mk, and st will compile without any loss of functionality because all the functions are included in libc on this platform. +## Backspace key does not work + +This is an issue that was discussed in suckless mailing list +<http://lists.suckless.org/dev/1404/20697.html>: + + Well, I am going to comment why I want to change the behaviour + of this key. When ascii was defined in 1968 communication + with computers were done using punched cards, or hardcopy + terminals (basically a typewritter machine connected with + the computer using a serial port). Due to this, ascii defines + DELETE as 7F, because in the puched cards, it means all the + holes of the card punched, so it is a kind of 'phisical + delete'. In the same way, BACKSPACE key was a non destructive + back space, as in typewriter machines. So, if you wanted + to delete a character, you had to BACKSPACE and then DELETE. + Other use of BACKSPACE was accented characters, for example + 'a BACKSPACE `'. The VT100 had no BACKSPACE key, it was + generated using the CONTROL key as another control character + (CONTROL key sets to 0 b7 b6 b5, so it converts H (code + 0x48) into BACKSPACE (code 0x08)), but it had a DELETE key + in a similar position where BACKSPACE key is located today + in common PC keyboards. All the terminal emulators emulated + correctly the difference between these keys, and backspace + key generated a BACKSPACE (^H) and delete key generated a + DELETE (^?). + + But the problem arised when Linus Torvald wrote Linux, and + he did that the virtual terminal (the terminal emulator + integrated in the kernel) returns a DELETE when backspace + was pressed, due to the fact of the key in that position + in VT100 was a delete key. This created a lot of problems + (you can see it in [1] and [2]), and how Linux became the + king, a lot of terminal emulators today generate a DELETE + when backspace key is pressed in order to avoid problems + with linux. It causes that the only way of generating a + BACKSPACE in these systems is using CONTROL + H. I also + think that emacs had an important point here because CONTROL + + H prefix is used in emacs in some commands (help commands). + + From point of view of the kernel, you can change the key + for deleting a previous character with stty erase. When you + connect a real terminal into a machine you describe the + type of terminal, so getty configure the correct value of + stty erase for this terminal, but in the case of terminal + emulators you don't have any getty that can set the correct + value of stty erase, so you always get the default value. + So it means that in case of changing the value of the + backspace keyboard, you have to add a 'stty erase ^H' into + your profile. Of course, other solution can be that st + itself modify the value of stty erase. I have usually the + inverse problem, when I connect with non Unix machines, and + I have to press control + h to get a BACKSPACE, or the + inverse, when a user connects to my unix machines from a + different system with a correct backspace key. + + [1] http://www.ibb.net/~anne/keyboard.html + [2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html + -- 1.8.5.3
