1. Week 9 – Lesson 2 Input & Output of Character Strings
IPC144
Week 9 – Lesson 2 Input & Output of Character Strings

2. Displaying Character Strings
In the previous lesson, we could use a for loop with the format specifier “%c” to display each element of the array, since a character string is an “array of characters”.
#include<stdio.h> #define SIZE
main() { int i; word1[SIZE] = “hello”; for (i=0; i < SIZE; i++)‏
printf (“%c “, word1[i]);
printf (“\n\n”); }

3. Displaying Character Strings
The printf() statement also allows the “%s” format specifier to display the entire character string that is stored in an array of characters.
This is extremely convenient since you do NOT require a for loop to display each element in the array of characters. eg. printf (“%s\n\n”, word1);

4. Displaying Character Strings
The “%s” format specifier has additional string alignment and formatting features:
“%s” - right justify (0 character offset) “%-s” - left justify (0 character offset) “%25s” - right justify (25 character offset) “%-25s” - left justify (25 character offset)‏
“%-25.15s” - left justify (display no more than characters)

5. Inputting Character Strings
The “%s” format specifier can also be used to read into an array when using the scanf() statement.
Note: Since when passing an array to a function, it actually passes a “pointer” to that array, you do NOT use the & symbol. Limitation: “%s” alone does not read multiple words (i.e. words delimited by a space, etc..)‏
eg char word[SIZE+1]; scanf(“%s”, word);

6. Inputting Character Strings
The “%[]” format specifier is used to read in a string, but characters within the square brackets are allowed, and the symbol ^ followed by characters within [] indicates any string except those characters.
“%[yYnN]”
“%[^0-9]”
In this case, if any character not allowed in above examples, then scanning of input stops, and the string value will be terminated...

7. Inputting Character Strings
The “%[^\n]” format specifier can solve the previous problem of scanning multiple words (i.e. reading in white space characters like space).
The following method is useful to read a character string with multiple words, but not to include <ENTER> or new-line
eg char word[SIZE+1]; scanf(“%[^\n]”, word);

8. Inputting Character Strings
The “%[]” format specifier can also specify how many characters to accept in a line.
eg.
“%30[^\n]” If more than 30 characters entered, then when <ENTER> is pressed, only first 30 characters assigned to string...

9. Inputting Character Strings
When using scanf with “%s” or “%[^\n]” format specifiers, a function should be created to clear the “\n” character that is stored for the next read.
This clearInput function should be called immediately after using scanf function to read in a string.

10. Inputting Character Strings
void clearInput(void)‏ {
while(getchar() != '\n')‏ ; }
printf ("Please enter string #1: ");
scanf ("%[^\n]", x);
clearInput();
printf ("Please enter string #2: ");
scanf ("%[^\n]", y);

11. Inputting Character Strings
The gets() function is like the getchar() function, except gets() reads in the entire string.
eg. gets(name);
Similar to scanf(“%[^\n]\n”, name);
gets does not know the number of characters passed into the array, so allow a sufficient size to store characters into the array! It might be better to stick to scanf, or functions like getchar() to build a more robust string entry function (see next slide)...

12. Inputting Character Strings
void getString(char x[])‏ {
int n=0;
char c;
while('\n' != (c = getchar()))‏
if (n < SIZE)‏
x[n++] = c;
x[n] = '\0';
} /* End of getString function */

13. Additional Resources Here are some Related-Links for Interest Only: