使用fscanf检测带引号的字符串

Question

I want to read in C the content of a file like this:

foo="bar"
alice="bob"
fruit="pineapple"

And I am interested in the specific value associated with the key alice , but without the surrounding quotes. So, I want bob .

So, I've written something like this

EDIT: Added printf of key/value

char key[20];
char value[20];
char output[20];

memset(key, 0, 20);
memset(value, 0, 20);

while(fscanf(fd, "%19[^=]=\"%19[^\"]\"", key, value) != EOF) {

    printf("%s=%s", key, value);

    if (strcmp(key, "alice") == 0) {
      memset(output, 0, 20);
      strncpy(output, value, 20);
      break;
    }

    memset(key, 0, 20);
    memset(value, 0, 20);
}

The problem is the strcmp never returns 0. So, the comparation between any key and "alice" is always false. And I'm getting this output:

foo=bar
alice=bob
fruit=pinneaple
=pineapple

Also tested the length of each key, by strlen, and it's correct. Apart from the last line of rubish, I get what I expect. So, I don't really understand...

Is there any obvious error here? I'm trying to debug the code, but I'm working with a target system very limited (openwrt), and I don't have access to gdb (actually, the code is cross-compiled in another machine, because my target one doesn't even have a compiler).

Any help is appreciated.

Answer 1

Do not use scanf() for user input (even when it comes from a file). Prefer fgets() .

Your immediate problem is with whitespace.

The contents of the file include '\\n' . The '\\n' are included in key .

If you want to keep using fscanf() try adding some spaces inside the conversion string:

while (fscanf(fd, " %19[^=]= \"%19[^\"]\"", key, value) == 2) /* ... */;
//                 ^        ^ (2nd one isn't as important)

Also notice I changed the condition. Rather than testing against EOF , test for a return value of 2 .