Filtering out comments.

[codevyper]

I have a block of code that reads a file line by line looking for a specific character combination contained within the line. It works fine.

while (fgets(line, sizeof(line), file ) != NULL) {
    match = strstr(line, CHECKSTR);
    if (match == NULL) {
        // Line does not contain substring 
    }
    else {
        // Line contains the substring
    }
}

What I want to do though is skip over any line that is a comment, since some lines that are commented out, may contain the substring I'm trying to match. The comment character is the standard # character, but I have to take into account that it may not be the first character on the line. The line could, for example be indented with spaces or tabs before the comment character occurs.

So I'm now thinking about the best way to go about this. I could either loop through a series of strcmp to determine whether or not I hit any other character besides a whitespace character or the # character, or I could try to use strok() to accomplish this. I need to read up on that function more. I'm still a noob.

So my question is what's the best way to go about this? Best being most efficient. I'm not asking for code, just how would you go about that if you had to do this?

Thanks

[CommonTater]

Ok so the comment character (an octothorpe) has to be the first non-whitespace character on a line...

int IsComment(char *str)
  { char *ptr = str;
     // advance to first non-whitespace character
     while(isspace(*ptr++));
     // is this a comment?
     if (*ptr) == '#'
       return 1;  // true
    return 0; }  // false


// read in a line from the file
if (! IsComment(Line))
  { //do what ya gotta do 
}

When you think in small blobs things get alot easier.

[Subsonics]

You could just ignore the line by doing nothing once you have identified it with something like this.

if( strchr(line, '#') )
    ;

[laserlight]

You could just ignore the line by doing nothing once you have identified it with something like this.

That won't actually work though, since it will ignore all lines with a comment, even those that contain uncommented out code. Furthermore, if '#' can occur in a context other than a comment, such a line will also be ignored.

[Subsonics]

Yes, that is the most simple example, it wasn't clear from the post what was the requirement. You could follow it up by a stpbrk() call if there are required characters such as ; in C for a valid line.