How do I trim leading/trailing whitespace in a standard way?

Question

Is there a clean, preferably standard method of trimming leading and trailing whitespace from a string in C? I\'d roll my own, but I would think this is a common problem wit

Answer 1

I didn't like most of these answers because they did one or more of the following...

1. Returned a different pointer inside the original pointer's string (kind of a pain to juggle two different pointers to the same thing).
2. Made gratuitous use of things like strlen() that pre-iterate the entire string.
3. Used non-portable OS-specific lib functions.
4. Backscanned.
5. Used comparison to ' ' instead of isspace() so that TAB / CR / LF are preserved.
6. Wasted memory with large static buffers.
7. Wasted cycles with high-cost functions like sscanf/sprintf.

Here is my version:

void fnStrTrimInPlace(char *szWrite) {

    const char *szWriteOrig = szWrite;
    char       *szLastSpace = szWrite, *szRead = szWrite;
    int        bNotSpace;

    // SHIFT STRING, STARTING AT FIRST NON-SPACE CHAR, LEFTMOST
    while( *szRead != '\0' ) {

        bNotSpace = !isspace((unsigned char)(*szRead));

        if( (szWrite != szWriteOrig) || bNotSpace ) {

            *szWrite = *szRead;
            szWrite++;

            // TRACK POINTER TO LAST NON-SPACE
            if( bNotSpace )
                szLastSpace = szWrite;
        }

        szRead++;
    }

    // TERMINATE AFTER LAST NON-SPACE (OR BEGINNING IF THERE WAS NO NON-SPACE)
    *szLastSpace = '\0';
}