c：使用while（scanf（）== 1）读取输入不会离开循环

Question

I'm reading from stdin into an array input[], but it never leaves the loop after reading the input and keeps expecting more input. What am I doing wrong?

        char input[1000];
        while(scanf("%s",input)==1){
            printf("%s\n",input);
        }

Answer 1

What you expect, how do you try to terminate it? scanf("%s", input) keeps waiting input always and always returns 1 if stdin is life, it skips whitespaces and matches the first char sequence without whitespaces. Please read the manual carefully.

If you want to continue scanf using then you should provide a special string for breaking the loop.

Answer 2

Since scanf() returns **the number of elements successfully read, you must find a way to make it fail to read the %s . One common practice is to end the input with EOF, which is Ctrl-Z then Enter in Windows console, and Ctrl-D on a Unix terminal. After reading EOF scanf() will return EOF which is of course not 1, then the loop exits normally.

Alternatively, you can use a custom terminating string in your code:

    char input[1000];
    while (scanf("%s", input) == 1) {
        if (strcmp(input, "end") == 0) {
            // End the loop
            break;
        }
        printf("%s\n", input);
    }