CODEWITHSUNDEEP
cfile-ioscanf
darksky
darksky

Reputation: 21019

fscanf a file with doubles and characters

I have a file which will contains basic mathematical operations. An example:

1 + 23 / 42 * 23

I am scanning the file, putting each "element" into a struct and pushing it onto a stack I created. The problem I have is as follows:

char reading;
while(!feof(fp)) {
  fscanf(fp, "%c", &reading);
  ....

This will scan 1, +, 2, 3 instead of 1, +, 23. What are other suggestions to use one fscanf and have it iterate and read all the inputs as intended to with respect to their type?

Regards,

Upvotes: 1

Views: 142

Answers (2)

qwertz
qwertz

Reputation: 14792

You should use fscanf() a bit different, like this:

char buf[16];
int val;
char op;

while (!feof(fp)) {
    fscanf("%s ", buf); // Note: Without ' ' the last value would be readed twice
    if (buf[0] == '+' || buf[0] == '-' || buf[0] == '/' || buf[0] == '*') {
        op = buf[0];
        // do something with op
    } else {
        sscanf(buf, "%d", &val);
        // do something with val
    }
}

The size of buf must be something which could store the length of your numbers.

Upvotes: 0

Ned Batchelder
Ned Batchelder

Reputation: 375634

fscanf is the wrong tool for this job, because it needs a format string that knows in advance what format to expect. Your best bet is to read a character at a time and build up tokens that you can then interpret, especially if you'll have to accept input like 2+2 (no spaces), or (1 + 23) / 42, with parentheses.

Upvotes: 1

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