[^：]的含义：scanf中的格式字符串

Question

I found this in some code and could not understand what it does:

scanf("%[^:]:%[^:]:%[^:\n]", a, b, c);

There was no mention of the [^:]: format string in the C documentation and I am quite confused.

Answer 1

The format string %[..] is for specifying the possible characters. For example %[A-DF] is for A, B, C, D, and F. And the ^ at the beginning is for any character excluding the characters specified. Hence, the first format string is for reading characters excluding colon. And the next is colon, and so on. You may test the scanf for the following input:

Adam:And:Apple

Answer 2

Important thing you should remember is, scanf() function accepts the arguments how it is specified.

For example:

scanf("%d %d",&a,&b); assuming a and b are integer.

In the command line you have to input a and then followed by space and then b.because you have given a space in-between two "%d's". if you are giving n number of spaces are other character then you have to enter in-between those character before the value gets accepted.

Hence in your case:

you enter the string not containing ":" in it.

Consider this case, if you want to enter a string containing ":" in it.

For example:

"some:init" is the string then, in first %[^:] the string "some" is stored,then comes the ":" and then in second %[^:] it stores init. Then it wait for one more ":" and then the string not containing ":".

ultimately accepting the input in this format doesn't fetch any thing.

The only thing matters is how you print it on to the console.