What techniques are available to test if a character string is all spaces?

char *p = "   woohoo";

int condition = /* some calculation applied to p            */ 
                /* to look for all 0x20/blanks/spaces only  */ 

if (condition)
{
开发者_JAVA百科}
else
{
    printf("not ");
}

printf("all spaces\n");

One-liner:

int condition = strspn(p, " ") == strlen(p);

Slightly more optimized:

int condition = p[strspn(p, " ")] == '\0';

If you want a fast way to do this, the best thing that comes to my mind is to write your own function (I assume you only search for ' ' characters) .

int yourOwnFunction(char *str, char c) {
    while(*str != '\0' && *str != c) {
        str++;
    }
    return *str == '\0';
}

So you just have to test

if(yourOwnFunction(p,' ')) {
    ...
} else {
    ...
}

Correct me if I misunderstood something :)

Btw I didn't test it, but this should be in the worst case as fast as the other proposed method. If you just want a one-liner strager's (elegant) solution is the way to go!