C - Read string with integers from formatted text file

Question

I have a text file following this format:

Thing 1: 0 0 128
Other thing: 255 64 255
Something else: 32 32 8

I intend to add more to this file eventually but the format will remain the same. What I want to do is read everything before the colon into a string and everything after it as an integer. I've tried this:

fscanf((file = fopen("colors.txt", "r")) == NULL){
    return -1;
}

fscanf("%s: %d %d %d", colorStr, &r, &g, &b);

while(!feof(file)){
    printf("%s: %d %d %d", colorStr, r, g, b);
    fscanf(file, "%s: %d %d %d", colorStr, &r, &g, &b);
}

fclose(file);

However, I get this output:

Thing 1:: 0 0 0
0: 0 0 0
0: 0 0 0
128: 0 0 0

And so on. Ideally, the output should read like this:

Thing 1: 0 0 128
Other thing: 255 64 255
Something else: 32 32 8

How can I fix this? The colorStr , r , g , and b variables were set up earlier in the program.

Answer 1

The problem with your code is that the text contains spaces, which %s does not allow.

Changing the format string to %[^:] will fix this problem.

However, the code would remain vulnerable to buffer overrun. Make sure that your format string includes the max size of colorStr to prevent it:

char colorStr[100];
fscanf(file, " %99[^:]: %d %d %d", colorStr, &r, &g, &b);

Your code uses feof(file) , which is incorrect. You should put fscanf into loop header. This would let you remove the duplicate fscanf call before the loop:

while(fscanf(file, " %99[^:]: %d %d %d", colorStr, &r, &g, &b) == 4) {
    printf("%s: %d %d %d\n", colorStr, r, g, b);
}

Note the space in front of the leading % format specifier. It instructs fscanf to skip the trailing spaces and/or '\\n' from the previous line.

Demo.