C：使用read系统调用从stdin读取double

Question

I am asking how can I read a double, int or any other type from stdin using the read system call.

What I've done so far:

long val ;
ssize_t r;
r = read(STDIN_FILENO,&val,sizeof(long));
printf("%ld\n",val);

Any idea?

Answer 1

You are not being clear whether you want to read (a) the ASCII representation of a long, double, int or whatever (ie the string "0.12345", or (b) the binary representation of that value.

If you want to do (a), you need to use fscanf . See the above answer.

If you want to do (b), your code looks right to me. What is the 'bad result' you are having? Did you check for r<0 , then look at errno or use perror() .

I suspect the problem is you wanted to do (a), but have coded for (b).

Answer 2

Use stdio and scanf

See http://linux.die.net/man/3/scanf

This will be easier to use that a raw read

EDIT

Read what you are initially expecting then try the others until you get a hit.

Better still redesign the user interface so that this problem does not arise