Adding characters at the end of a string

Question

I am trying to add some characters at the end of a string using the following code. I am not getting the desired output.

#include<stdio.h>        
#include<stdlib.h>       
#include<string.h>       
int main()   
{   
 int l,i;   
 char a[30];   
 printf("Enter \n");      
 scanf("%s",a);      
 l=strlen(a);      
 for(i=l;i<(29-l);i++)       
  {       
   scanf("%c",&a[i]);       
   a[i+1]='\0';      
   printf("\n%s",a);       
  }     
return 0;       
}     

Answer 1

I guess, the problem is with whitespace. After you enter the first string, there is still a newline \\n in the input buffer. When you then read one character with scanf , you get the newline and not the character you entered.

You can skip the whitespace, when you prefix the format string with a space

scanf(" %c",&a[i]);

Now it will append the character entered at the end of the string.

Update:

From scanf

The format string consists of a sequence of directives which describe how to process the sequence of input characters.
...
• A sequence of white-space characters (space, tab, newline, etc.; see isspace(3)). This directive matches any amount of white space, including none, in the input.

This means, when you insert a space in the format string, it will skip all white-space in the input.

This will happen automatically with other input directives like %s or %d . But %c takes the next character, even if it is a white-space char. Therefore, if you want to skip white-space in this case, you must tell scanf by inserting a space in the format string.