Some old snippets

ascii.c

/* ~ write all ascii characters into a file~ 
Is this program useful? NO!!! It's an obfuscated program that does nothing!!!*/
#include <stdio.h>
main(){FILE*f=fopen("ASCIITABLE.txt","w");char i=0x0;while
(f!=NULL){putc(i,f);if(i==0x7E){break;}else{i++;}}fclose(f);}

echo_char.c

#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <unistd.h>
#include <signal.h>

/*

Info:
This program outputs the actual char (received from keyboard) and shows it as char and decimal.
It is useful for escape sequences, like the function buttons on the keyboard (F1, F2, ..., F12)
or e.g arrow keys, etc...

Licensing:
 Copyright 2016 Lukas Himsel <lukas.himsel@web.de>
  
 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; either version 2 of the License, or
 (at your option) any later version.
 
 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.
 
 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 MA 02110-1301, USA.

*/

const char *table[33] = {
	"NUL", "SOH", "STX", "ETX", "EOT", "ENQ", "ACK", "BEL",
	"BS", "TAB", "LF", "VT", "FF", "CR", "SO", "ST", "DLE",
	"DC1", "DC2", "DC3", "DC4", "NAK", "SYN", "ETB", "CAN",
	"EM", "SUB", "ESC", "FS", "GS", "RS", "US", "SPACE"
}; 

/* 
first 32 (non-printable [invisible] characters from ASCII table)

Dec   Char   Description
 0    NUL    null
 1    SOH    start of heading
 2    STX    start of text
 3    ETX    end of text
 4    EOT    end of transmission
 5    ENQ    enquiry
 6    ACK    acknowledge
 7    BEL    bell
 8    BS    backspace
 9    TAB    horizontal tabulator
 10    LF    NL line feed (enter, new line)
 11    VT    vertical tab.
 12    FF    NP from feed, new page
 13    CR    carriage return
 14    SO    shift out
 15    ST    shift in
 16    DLE    data link escape
 17    DC1    device control 1
 18    DC2    device control 2
 19    DC3    device control 3
 20    DC4    device control 4
 21    NAK    negative acknowledge
 22    SYN    synchronous idle
 23    ETB    end of trans. block
 24    CAN    cancel
 25    EM    end of medium
 26    SUB    substitute
 27    ESC    escape
 28    FS    file separator
 29    GS    group separator
 30    RS    record separator
 31    US    unit separator
 32    SPACE    whitespace
 
*/

static int getch(void);

int main(){
	int c=0;
	while(1){
		c=getch();
		if(c < 33){
			printf("\033[31m%s\033[0m, %d\n", table[c], c);
		} else{
			printf("\033[32m%c\033[0m, %d\n", c,c);
		}
	}
	return 0;
}

/* getch function from github.com/lukas-h/getch.c */

static struct termios _term;

static void on_signal (int signal){
  tcsetattr(STDIN_FILENO, TCSANOW, &_term);
  exit(1);
}

int getch (void){
  int c = EOF;
  struct termios term, ttmp;

  tcgetattr(STDIN_FILENO, &term);

  tcgetattr(STDIN_FILENO, &_term);

  ttmp = term;

  ttmp.c_lflag &= ~(ICANON|ECHO);
  tcsetattr(STDIN_FILENO, TCSANOW, &ttmp);

  signal(SIGABRT, on_signal);
  signal(SIGINT, on_signal);
  signal(SIGKILL, on_signal);
  signal(SIGQUIT, on_signal);
  signal(SIGSTOP, on_signal);
  signal(SIGTERM, on_signal);

  c = getchar();

  tcsetattr(STDIN_FILENO, TCSANOW, &term);

  return c;
}

nroot.c

#include <math.h>
double nroot(double x, double n){ return pow(x, (1/n)); }