scanf doesn't put a terminating null byte

Question

I am reading a string from stdin using the scanf function.

char inputWord[100];
scanf("%99[^\n]", inputWord);

This works fine except the case when the first character in the input sequence is a newline (entered by pressing the enter key ). When I print the length of inputWord using strlen , it prints 6 (always) and when I print the inputWord string itself, it prints some garbage. man page of scanf states that a terminating null byte is added after the first match of a character in the input sequence with the set of excluded characters which here is [^\\n] . Why is it not adding a null byte in this case? Is it because scanf cannot match any character in this case (return value is zero)?

I know I should be using fgets but I am just curious to know the behaviour of scanf in this case. Seems like scanf is one beast of a function.

Answer 1

在这种情况下， scanf()的返回码将为0，因为它与转换规范的任何内容都不匹配（因为转换规范没有匹配，nothign会写入相应的变量）。