而不是告诉你答案的不的使用 scanf（）的 ，你可以在 的扫描集选项scanf（）的：

  scanf函数（％99 [^ \\ n]，评论）; //这将读取到字符串：评论
                           //一切从下一个99个字符，直到
                           //它得到一个换行符
 

I want to write a sub-program in which a user can input their comment. I use scanf("%s", X) and let them input a comment, but it can only store the word before a space bar in the string.

How can I solve this problem in order to store a whole sentence into a string or a file?

My code is presented below:

FILE *fp;
char comment[100];
fp=fopen("comment.txt","a");
printf("You can input your comment to our system or give opinion to the musics :\n");
scanf("%s",comment);
fputs(comment,fp);

Rather than the answers that tell you not to use scanf(), you can just the the Negated scanset option of scanf():

scanf("%99[^\n]",comment); // This will read into the string: comment 
                           // everything from the next 99 characters up until 
                           // it gets a newline