Thread: How to terminate a loop if user inputs blank space in a string or just press enter

The problem lies with your format string: " %[^\n]s". You need to remove the leading space, otherwise it would match whitespace until a character other than '\n' is encountered, hence it would keep waiting for input when you press enter.

Related to this is your use of malloc:

Code:

char *str;
int len = 1;
str = malloc(sizeof(char*) * len);

You're creating an array of 1 char, so it can only store the empty string, i.e., you have buffer overflow problems. I suggest that you go with a fixed size array that is reasonable large, e.g.,

Code:

char str[100];

This way, you can write:

Code:

while (scanf("%99[^\n]", str) == 1) {

Where the 99 indicates that a maximum of 99 characters can be read and stored in the array. I removed the trailing "s". You would need to insert a getchar() say at the start of the loop to get rid of the newline character from entering the line though.

Also, it looks like you have something weird here:

Code:

    if(*str == string.Empty){
        break;
    }

You can just get rid of this.

Code:

  int len = 1; 
  str = malloc(sizeof(char*) * len);
  printf("\nEnter The String : ");
 
 
  while(scanf(" %[^\n]s", str) == 1)

Given that you've made 3 mistakes in as many lines, I'll suggest an alternative
1. You use the wrong type in the sizeof - you want char, not char*
2. You only allocate a single char - which is not enough to contain a useful string and it's trailing \0
3. Your scanf blocks on newlines, but there is no other code to remove a newline from the input stream.

Start with this

Code:

char buff[BUFSIZ];
while ( fgets(buff,BUFSIZ,stdin) != NULL ) {
  // do stuff
}