c - How do I replace multiple spaces with a single space?

Question

Well I'm looking for a function that reduce multiple space characters ' ' in a string.

For example for string s given :

s="hello__________world____!"

The function must return "hello_world_!"

In python we can do it via regexp simply as:

re.sub("s+", " ", s);

Answer 1

A version that modifies the string in place, run it on a copy if the original must be preserved:

void compress_spaces(char *str)
{
    char *dst = str;

    for (; *str; ++str) {
        *dst++ = *str;

        if (isspace(*str)) {
            do ++str; 

            while (isspace(*str));

            --str;
        }
    }

    *dst = 0;
}