#include <stdio.h> 
 #include <stdlib.h>
 #include <string.h>
 #include <stdbool.h>

void strrev(char *str) // turn a character string back to front
{
    char *end, tmp;

    end = str + strlen(str) - 1;

    for (; end > str; --end, ++str) {
        tmp = *end;
        *end = *str;
        *str = tmp;
    }
}
void flipper ()

// remove the first '5' from a number. So 1525354 becomes 125354 while 
// -1525354 becomes -152534. Assume 5 is included in the input

{
  int original=1;
  int i, j;
  bool nego;
  bool found;
  char tstr[20];
  char* tptr;
  char* nptr;
  char match[] = "5";

  while (original != 0)              // Some exit criteria
  {
    printf("Enter an integer: ");    // Ask for a number
    scanf("%d", &original);
    sprintf( tstr, "%d", original);  // push the number into a string
    nego=(original < 0);
    if (nego==true)                  // different behaviour for a -ve number
    {
        sprintf( tstr, "%d", abs(original));
        strrev( tstr);               // reverse the digits
    }
    tptr=tstr;

    nptr = (char*)malloc(strlen(tptr)-1); // somewhere to hold the new string

    i=0;
    found=false;
    while (*tptr)                    // search for the digit to be removed
    {
       if ( (strstr(tptr, match) == tptr) &&
            (found==false) ) 
       {
         found=true;
         tptr++;
       }
       else
       {
         nptr[i++] = *tptr++;        // this is not the digit so save it
       }
    }

    if (nego == true)                // if this was a negative number
    {                                // reverse again and make negative
        strrev( nptr);
    }
    sscanf(nptr, "%d", &j);
    if (nego == true)
    {
        j = (-j);
    }
    printf("and we get %d\n", j);
  }
}
int main()   // declare main as int.
{
  
   flipper();
   return 0;
}

void remove_first_occurance(char haystack[], char needle);
void remove_last_occurance (char haystack[], char needle);

    sprintf(buff, "%d", num);
    if (num<0) remove_last_occurance (buff, '5');
    else       remove_first_occurance(buff, '5');

// remove_digit.c

#define _POSIX_C_SOURCE 200809L

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int remove_digit( int n, char digit )
{
	// if 'n' is positive: remove the first occurrence of 'digit'.
	// if 'n' is negative: remove the last occurrence of 'digit'.

	char in_buf[16];
	char out_buf[16];
	char *digit_ptr;

	if ( digit < '0' || digit > '9' )
		return n;

	sprintf(in_buf, "%d", n);

	if ( n < 0 )
		digit_ptr = strrchr(in_buf, digit);
	else
		digit_ptr = strchr(in_buf, digit);

	if ( digit_ptr )
	{
		*digit_ptr++ = '\0';

		char *dst = out_buf;
		dst = stpcpy(dst, in_buf);
		dst = stpcpy(dst, digit_ptr);
		n = atoi(out_buf);
	}

	return n;
}


int main( int argc, char *argv[] )
{
	for ( int i = 1 ; i < argc ; i++ )
	{
		int n = atoi(argv[i]);
		printf("Arg: %11d  Result: %11d\n", n, remove_digit(n, '5'));
	}

	return 0;
}

#include <stdio.h>
char a_short_string[30]="Something to overwrite";
char next_string[150]="Here we have really important information!";
int main()
{       
        char too_long_message[]="123456789012345678901234567890 Oh my God! this" 
               " message is too long to fit in that short string!!";
        sprintf(a_short_string, "%s\n", too_long_message);
        printf("short_string %s\n", a_short_string);
        printf("next_string: %s\n", next_string);
        return 0;
}