Dave's Brain

Browse - programming tips - delete non numeric characters from a string

Date: 2009mar28
Language: C/C++

Q.  How can I delete non-numeric characters from a string?

A.  Yes, this is handy user-entered strings that are supposed to be numbers.
Use the function DeleteNonNumericCharacters() below:

// helper function
inline char *Shuffle(char *dest, const char *src)
{
	return (char *) memmove(dest, src, strlen(src) + sizeof(char));
}

// helper function
inline bool IsNumeric(const char c)
{
	return isdigit(c) || c == '-' || c == '.';
}

void DeleteNonNumericCharacters(char *s)
{
	for (char *p = s + strlen(s) - 1; p >= s; p--)
	{
		if (!IsNumeric(*p))
		{
			Shuffle(p, p+1);
		}
	}
}

void ExampleUse()
{
	char	buf[100];

	lstrcpyn(buf, "EDT5EST", sizeof(buf));
	DeleteNonNumericCharacters(buf);

	printf("buf=%s<\n", buf);
	// Prints out "5"

	// Now you can safely do atoi() on it:
	int hours = atoi(buf);
}

Add a comment

Sign in to add a comment