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| -rw-r--r-- | FAQ | 87 |
1 files changed, 43 insertions, 44 deletions
@@ -104,54 +104,53 @@ 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). + of this key. When ASCII was defined in 1968, communication + with computers was done using punched cards, or hardcopy + terminals (basically a typewriter machine connected with the + computer using a serial port). ASCII defines DELETE as 7F, + because, in punched-card terms, it means all the holes of the + card punched; it is thus a kind of 'physical delete'. In the + same way, the BACKSPACE key was a non-destructive backspace, + as on a typewriter. So, if you wanted to delete a character, + you had to BACKSPACE and then DELETE. Another use of BACKSPACE + was to type 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 + the BACKSPACE key is located today on common PC keyboards. + All the terminal emulators emulated the difference between + these keys correctly: the backspace key generated a BACKSPACE + (^H) and delete key generated a DELETE (^?). + + But a problem arose when Linus Torvalds wrote Linux. Unlike + earlier terminals, the Linux virtual terminal (the terminal + emulator integrated in the kernel) returned a DELETE when + backspace was pressed, due to the VT100 having a DELETE key in + the same position. This created a lot of problems (see [1] + and [2]). Since Linux has become the king, a lot of terminal + emulators today generate a DELETE when the backspace key is + pressed in order to avoid problems with Linux. The result is + that the only way of generating a BACKSPACE on these systems + is by using CONTROL + H. (I also think that emacs had an + important point here because the 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 + connect a real terminal into a machine you describe the type + of terminal, so getty configures the correct value of stty + erase for this terminal. In the case of terminal emulators, + however, 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. + For this reason, it is necessary to add 'stty erase ^H' to your + profile if you have changed the value of the backspace key. + Of course, another solution is for st itself to modify the + value of stty erase. I usually have the inverse problem: + when I connect to non-Unix machines, I have to press CONTROL + + h to get a BACKSPACE. The inverse problem occurs 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 |