Question

I am attempting to parse a text (CSS) file using fscanf and pull out all statements that match this pattern:

@import “some/file/somewhere.css”;

To do this, I have the following loop set up:

FILE *file = fopen(pathToSomeFile, "r");
char *buffer = (char *)malloc(sizeof(char) * 9000);

while(!feof(file))
{
    // %*[^@] : Read and discard all characters up to a '@'
    // %8999[^;] : Read up to 8999 characters starting at '@' to a ';'.
    if(fscanf(file, "%*[^@] %8999[^;]", buffer) == 1)
    {
        // Do stuff with the matching characters here.
        // This code is long and not relevant to the question.
    }
}

This works perfectly SO LONG AS the VERY FIRST character in the file is not a ‘@’. (Literally, a single space before the first ‘@’ character in the CSS file will make the code run fine.)

But if the very first character in the CSS file is a ‘@’, then what I see in the debugger is an infinite loop — execution enters the while loop, hits the fscanf statement, but does not enter the ‘if’ statement (fscanf fails), and then continues through the loop forever.

I believe my fscanf formatters may need some tweaking, but am unsure how to proceed. Any suggestions or explanations for why this is happening?

Thank you.

Answer 1

Your format string does the following actions:

• Read (and discard) 1 or more non-@ characters
• Read (and discard) 0 or more whitespace characters (due to the space in the format string)
• Read and store 1 to 8999 non-; characters

Unfortunately, there is no format specifier for reading “zero or more” characters from a user-defined set.

If you don’t care about multiple @include statements on a line, you could change your code to read a single line (with fgets), and then extract the @include statement from that (if the first character does not equal @, you can use your current format string with sscanf, otherwise, you could use sscanf(line, "%8999[^;]", buffer)).

If multiple @include statemens on a line should be handled correctly, you could inspect the next character to be read with getc and then put it back with ungetc.