sscanf problems ...

Hi im currently reading "teach yourself C in 21 days" from SAMS. I'm at chapter 14 "working with the screen, printer and keybord).

Well i decided to do some testing with sscanf. I have this file with this contents:

Code:

A807091452|11571719|+2.168403E-07|T|P
A807091454|11571719|+2.170490E-07|T|P
A807091454|11550661|+2.113044E-07|T|P

This is the code:

Code:

int get_mean(FILE *fp)
{
     int i = 0;
     
     char  date[MAX+1],
		  serial[MAX+1],
		  measure[MAX+1],
		  buff[MAX+1];
     float mes;
     
     
     while( (fgets(buff, 100, fp)) != NULL) {
         sscanf(buff, "%*c %[1234567890] %*c %[1234567890] %*2c %2.2f ", date, serial, &mes);
         printf("%s %s %f\n", date, serial, mes);
     } 
    return 0;
}

In my opinion the fisrt "A" is read bij %*c, the next string "807091454" bij %[1234567890] the "|" by %*c, then "11571719" by %[1234567890] "|+" by %*2c and then the float "2.168403".

But is does not do what i expect i to do...
when i run the program this comes out:

Code:

807091452 11571719 0.000000
807091454 11571719 0.000000
807091454 11550661 0.000000

Can somebody give me a clue ?

You can't fit 2.2 into a scanf specification (i.e., no fair specifying precision -- you can specify field width). So it's trying to match the literal characters "%2.2f".

Do you know that you can check the return value of scanf?
as well as %n format to check at what position the successfull scanf was finished?

Thx for helping!. I use "%8f" for the float and now it works just fine. Using the return value of scanf is also a good tip, i did know it but did not think about it. As a newbe i have a lot to remember .

Originally Posted by pic-o-matic

Thx for helping!. I use "%8f" for the float

adding width specifier to formats used for parsing string data seems even more important to avoid buffer overruns

> while( (fgets(buff, 100, fp)) != NULL)
Where did 100 come from?
Why not sizeof(buff) instead?