Question

In some CGI code, I need to encode rarely-occurring ‘&’, ‘<‘, and ‘>’ chars. In the encoding function, I want to get out right away if there are no such chars in the input string. So, at entry, I try to use strtok( ) to find that out:

char *
encode_amp_lt_gt ( char *in ) {
  ...
  if ( NULL == strtok( in, "&<>" )) {
    return in;
  }
  ...
}

But, even in the absence of any of the delimiters, strtok( ) returns a pointer to the first character of in.

I expected it to return NULL if no delims in the string.

Is my code wrong, or is my expectation wrong? I don’t want to call strchr( ) three times just to eliminate the usual case.

Thanks!

Answer 1

The function you want is strpbrk, not strtok. The bigger question is – how is the string that is being returned being allocated when you’re replacing things, and how does the calling function know if it should free it or not?