How can I translate Linux key codes from / dev / input / event * to ASCII in Perl?

Question

I am writing a Perl script that reads data from the infamous /dev/input/event* , and I have not found a way to translate the key codes generated by the kernel into ASCII.

I am talking about linux key codes in this table here , and I cannot find anything that would help me translate them without hard coding the array in a script. Am I missing something?

I would like to skip part of the array because it doesn't seem to be good practice, so any idea? :)

Answer 1

This is basically a map issue. You must take the key code and find its ASCII equivalent. What about the "part of the array", what do you think is not good practice?

I have not seen a module for this on CPAN, but that means you have a chance to be the first to download it. :)

Answer 2

Unfortunately, I do not program in Perl, but here is a simple example written in C. Perhaps this may help you nonetheless.

 /* * Based on keytable.c by Mauro Carvalho Chehab * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, version 2 of the License. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <linux/input.h> #include <string.h> #include <linux/input.h> #include <sys/ioctl.h> #define KEY_RELEASE 0 #define KEY_PRESS 1 #define KEY_KEEPING_PRESSED 2 #include "parse.h" void prtcode(int codes) { struct parse_key *p; for (p = keynames; p->name != NULL; p++) { if (p->value == (unsigned) codes) { printf("scancode %s (0x%02x)\n", p->name, codes); return; } } if (isprint(codes)) { printf("scancode '%c' (0x%02x)\n", codes, codes); } else { printf("scancode 0x%02x\n", codes); } } int main (int argc, char *argv[]) { int i, fd; struct input_event ev[64]; if (argc != 2) { fprintf(stderr, "usage: %s event-device (/dev/input/eventX)\n", argv[0]); return 1; } if ((fd = open(argv[1], O_RDONLY)) < 0) { perror("Couldn't open input device"); return 1; } while (1) { size_t rb = read(fd, ev, sizeof(ev)); if (rb < (int) sizeof(struct input_event)) { perror("short read"); return 1; } for (i = 0; i < (int) (rb / sizeof(struct input_event)); i++) { if (EV_KEY == ev[i].type) { if ((ev[i].value == KEY_PRESS) || (ev[i].value == KEY_KEEPING_PRESSED)) { prtcode(ev[i].code); printf("type %d code %d value %d\n", ev[i].type, ev[i].code, ev[i].value); printf("\n"); } } } } return 0; } 

To create parse.h, put this in your Makefile :

 parse.h: /usr/include/linux/input.h @echo generating parse.h @echo -en "struct parse_key {\n\tchar *name;\n\tunsigned int value;\n} " >parse.h @echo -en "keynames[] = {\n" >>parse.h @more /usr/include/linux/input.h |perl -n \ -e 'if (m/^\#define\s+(KEY_[^\s]+)\s+(0x[\d\w]+|[\d]+)/) ' \ -e '{ printf "\t{\"%s\", %s},\n",$$1,$$2; }' \ -e 'if (m/^\#define\s+(BTN_[^\s]+)\s+(0x[\d\w]+|[\d]+)/) ' \ -e '{ printf "\t{\"%s\", %s},\n",$$1,$$2; }' \ >> parse.h @echo -en "\t{ NULL, 0}\n};\n" >>parse.h 

Then use it as follows:

 ./keytable /dev/input/by-path/platform-i8042-serio-0-event-kbd 

Answer 3

Example 1 returns only the same key code values ​​that already come from the linux kernel. For example, you get KEY_A 0x1e for pressing the "a" key. What you want (and what I want) is an ascii conversion, so if "a" is pressed, I want to see 0x61 for lowercase and 0x41 for uppercase.